Battery Monitoring System

ABSTRACT

A battery monitoring system, comprises a battery state detection circuit that detects battery states of a plurality of battery cells that are connected in series, based on respective cell voltages of the plurality of battery cells, and a control circuit that monitors state of a battery cell, based on each cell voltage of the plurality of battery cells. The control circuit inputs pseudo voltage information to the battery state detection circuit, and thereby diagnoses whether or not the battery state detection circuit is operating normally.

INCORPORATION BY REFERENCE

The disclosures of the following priority applications are hereinincorporated by reference:

Japanese Patent Application No. 2009-046082 filed Feb. 27, 2009

Japanese Patent Application No. 2009-079864 filed Mar. 27, 2009

Japanese Patent Application No. 2009-079863 filed Mar. 27, 2009

Japanese Patent Application No. 2009-179741 filed Jul. 31, 2009.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a battery monitoring system, and to amethod of diagnosis for a battery monitoring system.

2. Description of Related Art

With a hybrid automobile or an electric automobile or the like, in orderto ensure the desired high voltage, a group battery structure isemployed that includes a large number of battery cells that serve assecondary batteries, connected in series. With this type of groupbattery, in order to provide capacity calculation and protectionmanagement for each of the battery cells, management of the batterycells is performed using monitor ICs that monitor the states of thebattery cells and control ICs that control their charge/dischargestates. In particular, since there is a danger of an excessive chargestate occurring with a system that employs a lithium ion battery due tothe high energy density of such a lithium ion battery, accordingly, asdisclosed in Japanese Patent No. 4,092,580, the reliability and thesecurity are enhanced by the voltage of each of the cells being measuredby the control ICs and the monitor ICs so that any excessive chargestate is detected, and by it being arranged to stop the charge ordischarge of the battery if such an excessive charge state is detectedby any of the ICs.

The monitor ICs detect the voltages of each of the battery cellsindividually; for example, if there is some battery cell that is in anexcessive charge state, then excessive charge information is transmittedby communication with its corresponding control IC. And, in order toensure that such excessive charge information will be reliablytransmitted to the control ICs, by transmitting test signals from thecontrol ICs, diagnosis is performed for determining whether or not thereis any anomaly such as breakage of a communication line or the like.

Furthermore, when detecting the voltages of a battery cell, apredetermined battery cell is selected by a multiplexer, and its voltageis detected by a voltage detection unit. Thus, it is possible to detectthe voltages of all of the battery cells by changing over theconnections of the multiplexer. In order to acquire the correct cellvoltages, it is necessary for a cell voltage measurement circuitincluding the multiplexer to operate correctly. Due to this, in JapaneseLaid-Open Patent Publication 2008-92656, it has been proposed to comparetogether the sum of all of the individually measured values for thevoltages of all of the cells, and the measured value for the totalbattery voltage as measured by a total voltage measurement circuit, andto decide that there is some fault with the cell voltage measurementcircuit including the multiplexer, if there is a significant differencebetween these two.

However, in the above described excessive charge diagnosis process, itis not possible to proceed as far as diagnosing whether or not theexcessive charge detection circuitry internal to the monitor ICs isfunctioning normally, and this is a deficiency from the point of view ofenhancing the reliability. Furthermore, in the case of a system thatdecides upon whether or not there is a fault with the cell voltagemeasurement circuit by comparing together the sum of the individualvoltages of all of the cells and the total voltage of them all together,if for example an anomalous condition occurs in which the multiplexerselects one cell only, but the states of charge of all of the cells areuniform, then there is almost no difference between the sum of theindividual cell voltages and the total voltage, so that there is a fearthat an erroneous diagnosis of normal operation will be reached.Moreover, if a sudden voltage fluctuation occurs simultaneously with themeasurement of the voltage of one cell that is being selected by themultiplexer, then it may happen that this causes a difference betweenthe sum of all of the individual cell voltages and the voltage of themall together, so that there is a risk of an erroneous decision eventhough the multiplexer is actually operating correctly. Accordingly, inorder reliably to detect excess charging, as described above, it hasbeen necessary to enhance the reliability of the monitor ICs and thecontrol ICs separately.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a battery monitoringsystem, and a method of diagnosis for it, that can diagnose whether ornot the battery state detection circuitry is operating normally, so thatthe reliability of the battery monitoring system as a whole is enhanced.

In order to achieve the above mentioned object, the present invention, abattery monitoring system, comprises a battery state detection circuitthat detects battery states of a plurality of battery cells that areconnected in series, based on respective cell voltages of the pluralityof battery cells, and a control circuit that monitors state of a batterycell, based on each cell voltage of the plurality of battery cells. And,the control circuit inputs pseudo voltage information to the batterystate detection circuit, and thereby diagnoses whether or not thebattery state detection circuit is operating normally.

One diagnosis method of the present invention is a diagnosis method fora battery monitoring system that comprises an excessive charge detectioncircuit that detects excessive charge of a battery cell by comparingeach cell voltage of a plurality of battery cells that are connected inseries with an excessive charge threshold value, and outputs detectioninformation, wherein a voltage that corresponds to excessive charge isinputted to the excessive charge detection circuit instead of themeasured cell voltage, and whether or not the excessive charge detectioncircuit is operating normally is diagnosed based on presence or absenceof an output of the detection information.

Another diagnosis method of the present invention is a diagnosis methodfor a battery monitoring system that selects one of a plurality ofvoltages inputted from a plurality of battery cells that are connectedin series with a selection circuit, measures this selected voltage witha voltage measurement circuit, and monitors state of the battery cellbased on the measured voltage, wherein a plurality of mutually differentvoltages are generated, a mutually different voltage is selected by theselection circuit instead of a voltage of the battery cell, and state ofselection of the selection circuit is diagnosed based on voltage valuesmeasured by the voltage measurement circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a drive system for a rotatingelectrical machine of a vehicle;

FIG. 2 is a figure showing a portion of FIG. 1 in more detail, includingintegrated circuits IC1 through IC3 that are related to a battery block9A;

FIG. 3 is a figure schematically showing an internal block of one of theICs;

FIG. 4 is a figure for explanation of the timing of a measurementoperation;

FIG. 5 is a figure showing a digital circuit portion of the internalblocks of the IC shown in FIG. 3;

FIG. 6 is a figure showing a communication circuit 127 and explainingits operation;

FIG. 7A is a figure for explanation of connection diagnosis related to abattery cell BC1, and shows peripheral circuitry for detection of itscell voltage;

FIG. 7B is a figure for explanation of connection diagnosis related tothis battery cell BC1, and shows operations of various types when a maskfunction is ON and OFF;

FIG. 8A is a figure for explanation of connection diagnosis related to abattery cell BC2, and shows peripheral circuitry for detection of itscell voltage;

FIG. 8B is a figure for explanation of connection diagnosis related tothis battery cell BC2, and shows operations of various types when a maskfunction is ON and OFF;

FIG. 9A is a figure for explanation of connection diagnosis, andparticularly explains connection diagnosis related to a battery cellBC3;

FIG. 9B is a figure for explanation of connection diagnosis, andparticularly explains connection diagnosis related to a battery cellBC4;

FIG. 10A is a figure for explanation of connection diagnosis, andparticularly explains connection diagnosis related to a battery cellBC5;

FIG. 10B is a figure for explanation of connection diagnosis, andparticularly explains connection diagnosis related to a battery cellBC6;

FIG. 11 is a flow chart showing an example of multiplexer connectiondiagnosis;

FIG. 12 is a flow chart showing another example of multiplexerconnection diagnosis;

FIG. 13 is a figure for explanation of a second embodiment;

FIG. 14A is a figure for explanation of changeover operation betweenmultiplexers MUX1 and MUX2, and particularly shows a situation of a cellvoltage measurement mode;

FIG. 14B is a further figure for explanation of changeover operationbetween the multiplexers MUX1 and MUX2, and particularly shows asituation of a diagnosis mode;

FIG. 15A is a figure showing states of multiplexers MUX1 through MUX5and HVMUX1 and HVMUX2 and so on during cell voltage measurement andduring diagnosis, and particularly shows a case in which changeoverbetween the multiplexers HVMUX1 and HVMUX2 is performed by signals STG1and STG2;

FIG. 15B is a further figure showing states of the multiplexers MUX1through MUX5 and HVMUX1 and HVMUX2 and so on during cell voltagemeasurement and during diagnosis, and particularly shows a case in whichchangeover between the multiplexers HVMUX1 and HVMUX2 is performed bycommand from a microcomputer 30;

FIG. 16 is a figure for explanation of a variant of the secondembodiment, and shows internal blocks of an integrated circuit IC1;

FIG. 17 is a figure showing a relationship between combinations of inputterminals of the multiplexers HVMUX1 and HVMUX2, and voltage values thatare measured;

FIG. 18 is a figure for explanation of a third embodiment;

FIG. 19 is a figure for explanation of a fourth embodiment;

FIG. 20 is a figure for explanation of a fifth embodiment;

FIG. 21 is a figure for explanation of a sixth embodiment;

FIG. 22 is a figure showing characteristics of comparators COMP1 throughCOMP4;

FIG. 23 is a figure showing a seventh embodiment;

FIG. 24 is a figure showing a relationship between selection states ofmultiplexers HVMUX1 and HVMUX2 and ON/OFF states of balancing switches129A and 129B, and voltage values that are measured;

FIG. 25A is a figure showing an eighth embodiment, and particularlyshows a portion of the internal blocks of an IC;

FIG. 25B is a figure showing the structures of multiplexers MUX1 throughMUX4;

FIG. 26 is a flow chart showing steps of diagnosis;

FIG. 27 is a figure showing an example of a case in which a voltagesupply is provided externally to the IC;

FIG. 28 is a figure showing a structure for performing excessive chargedetection; and

FIG. 29 is a flow chart showing steps of excessive charge detectionfunction diagnosis;

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, embodiments of the present invention will be describedwith reference to the figures. First, structural elements that arecommon to all of these embodiments will be explained. FIG. 1 is a blockdiagram showing a drive system for a rotating electrical machine for avehicle. This drive system shown in FIG. 1 includes a battery module 9,a battery monitoring system 100 that monitors the battery module 9, aninverter device 220 that converts DC electrical power from the batterymodule 9 into three phase AC electrical power, and a motor 230 thatdrives the vehicle. The motor 230 is driven by the three phase AC powerfrom the inverter device 220. The inverter device 220 and the batterymonitoring device 100 are linked together by CAN communication, and theinverter device 220 functions as a higher level controller for thebattery monitoring device 100. Furthermore, the inverter device 220operates on the basis of command information from some yet higher levelcontroller, not shown in the figures.

The inverter device 220 includes a power module 226, a MCU (MotorControl Unit) 222, and a driver circuit 224 for driving the power module226. The power module 226 converts the DC power supplied from thebattery module 9 into three phase AC power for driving the motor 230. Itshould be understood that a smoothing capacitor of high capacity fromaround 700 μF to around 2000 μF is provided between high voltage linesHV+ and HV− that are connected to the power module 226, although thissmoothing capacitor is not shown in the figures. This smoothingcapacitor operates to reduce voltage noise to which the integratedcircuits included in the battery monitoring system 100 are subjected.

In the operation start state of the inverter device 220, the charge inthe smoothing capacitor is approximately zero, and when a relay RLcloses a large initial current flows into the smoothing capacitor. Andthere is a fear that the relay RL will suffer damage due to fusionbecause of this high current. In order to solve this problem, accordingto a command from a higher level controller, when starting to drive themotor 230, the MCU 222 changes a pre-charge relay RLP from its openedstate to its closed state, thus charging up the smoothing capacitor, andonly thereafter changes the relay RL from its opened state to its closedstate, thus starting the supply of power from the battery module 9 tothe inverter device 220. When charging up the smoothing capacitor, thischarging is performed while limiting the maximum current with a resistorRP. By performing this type of operation, not only is it possible toprotect the relay circuit, but also it is possible to reduce the maximumcurrent that flows in the battery cells and the inverter device 220 tonot more than a predetermined value, so that it is possible to maintainhigh security.

It should be understood that the inverter device 220 controls the phaseof the AC power generated by the power module 226 with respect to therotor of the motor 230, so that during vehicle braking the motor 230 canbe operated as a generator. In other words, regenerative braking controlis performed, and power that is generated by the operation of the motoras a generator is supplied on a regenerative basis to the battery module9, so as to recharge that battery module 9. If the state of charge ofthe battery module 9 has dropped with respect to a reference state, thenthe inverter device 220 operates the motor 230 as a generator. The threephase AC power that is generated by the motor 230 is converted into DCpower by the power module 226 and is then supplied to the battery module9. As a result, the battery module 9 is charged up.

On the other hand when, according to a command from the higher levelcontroller, the motor 230 is to be operated for power running, the MCU222 controls the driver circuit 224 so as to control the switchingoperation of the power module 226 to generate a rotating magnetic fieldthat leads with respect to the rotation of the rotor of the motor 230.In this case, the DC power from the battery module 9 is supplied to thepower module 226. Furthermore, when the battery module 9 is to becharged up by regenerative braking control, the MCU 222 controls thedriver circuit 224 so as to control the switching operation of the powermodule 226 to generate a rotating magnetic field that trails withrespect to the rotation of the rotor of the motor 230. In this case,power from the motor 230 is supplied to the power module 226, and DCpower from the power module 226 is supplied to the battery module 9. Asa result, the motor 230 is operated as a generator.

The power module 226 of the inverter device 220 performs powerconversion between DC power and AC power by performing switchingoperation to go continuous and go discontinuous at high speed. At thistime, since high currents are interrupted at high speeds, large voltagefluctuations are generated due to the inductance of the DC circuitry.The high capacity smoothing capacitor described above is provided inorder to suppress these voltage fluctuations.

The battery module 9 consists of two battery blocks 9A and 9B that areconnected in series. Each of these battery blocks 9A and 9B includes 16cells that are connected in series. The battery block 9A and the batteryblock 9B are connected in series via a service disconnector SD formaintenance and inspection in which a switch and a fuse are connected inseries. The direct connection of the electric circuit is interrupted byopening this service disconnector, and no current flows, even ifhypothetically it is supposed that a connection circuit becomesestablished between one point somewhere in the battery block 9A or 9Band the vehicle. It is possible to maintain high security with this typeof structure. Moreover, even if during inspection an operator shouldtouch both HV+ and HV− at the same time, it is ensured that his bodywill not be subjected to high voltage, so that safety is assured.

A battery disconnector unit BDU that includes the relay RL, the resistorRP, and the pre-charge relay RLP is provided in the high voltage lineHV+, between the battery module 9 and the inverter device 220. Theresistor RP and the pre-charge relay RLP are in a series circuit that isconnected in parallel with the relay RL.

The battery monitoring system 100 principally performs measurement ofthe voltage of each cell, measurement of the total voltage, measurementof the current, measurement of the cell temperatures, adjustment of thecapacities of the cells, and so on. For this, ICs (integrated circuits)IC1 through 106 are provided as cell controllers. The 16 battery cellsthat are provided within each of the battery blocks 9A and 9B aredivided into three cell groups, and one of these ICs is provided foreach of these six cell groups.

The integrated circuits IC1 through IC6 are provided with acommunication circuit 602 and a one-bit communication circuit 604. Inthe communication circuit 602 for transmitting cell voltage valuereadings and commands of various types, serial communication with amicrocomputer 30 is performed by the daisy chain method via insulatingelements (for example, photo-couplers) PH. And the one-bit communicationcircuit 604 transmits an anomaly signal when excessive charge of somecell has been detected. In the example shown in FIG. 1, thecommunication circuit 602 is divided into a higher level communicationpath to the integrated circuits IC1 through IC3 of the battery block 9A,and a lower level communication path to the integrated circuits IC4through IC6 of the battery block 9B.

Each IC performs anomaly diagnosis, and, if it has itself determinedthat an anomaly is present, or if it has received an anomaly signal fromanother one of the ICs at its reception terminal FFI (describedhereinafter; refer to FIG. 2), then it transmits an anomaly signal fromits transmission terminal FFO (described hereinafter; refer to FIG. 2).On the other hand, if an anomaly signal that it previously was receivingat its reception terminal FFI ceases to be received, or if it has itselfdetermined that an anomaly that it was detecting has ceased, then itstops transmitting this anomaly signal from its transmission terminalFFO. In this embodiment, this anomaly signal is a one-bit signal.

While the microcomputer 30 does not transmit any anomaly signal to theICs, in order to check that the one-bit communication circuit 604 (thatis the transmission path for the anomaly signals) is operatingcorrectly, it can output a test signal, that is a pseudo-anomaly signal,to the one-bit communication circuit 604. Upon reception of this testsignal, IC1 outputs an anomaly signal to the communication circuit 604,and this anomaly signal is received by IC2. And the anomaly signal istransmitted from IC2 to IC3, and then to IC4, IC5, and IC6 in order, andfinally is returned from IC6 to the microcomputer 30. If thecommunication circuit 604 is operating normally, then the pseudo-anomalysignal that was transmitted from the microcomputer 30 is returned to themicrocomputer 30 via the communication circuit 604. The microcomputer 30can diagnose the communication circuit 604 by sending a pseudo-anomalysignal in this manner, so that the reliability of the system isenhanced.

A current sensor Si such as a Hall element or the like is installed inthe battery disconnector unit BDU, and the output of this current sensorSi is inputted to the microcomputer 30. Signals related to the totalvoltage of the battery module 9 and to temperature are also inputted tothe microcomputer 30, and are each measured by A/D converters that areincluded in the microcomputer 30. Temperature sensors are provided at aplurality of spots upon the battery blocks 9A and 9B.

FIG. 2 is a figure showing a portion of FIG. 1 in more detail, includingthe integrated circuits IC1 through IC3 that are related to the batteryblock 9A of FIG. 1. It should be understood that a similar structure isalso provided in relation to the battery block 9B, although explanationthereof is omitted. The 16 battery cells that are provided to thebattery block 9A are divided into three cell groups that include 4cells, 6 cells, and 6 cells, and IC1, IC2, and IC3 are provided so as tocorrespond to these cell groups respectively.

The terminals CV1 through CV6 of IC1 are terminals for measuring thecell voltages of the battery cells; each of the IC can measure thevoltages of up to 6 cells. In the cases of IC2 and IC3 that monitor 6cells each, a resistor RCV is provided to each of the voltagemeasurement lines of each of the 6 terminals CV1 through CV6 in order toprotect the terminals and limit the discharge currents for capacityadjustment. On the other hand, in the cases of IC1 that monitors 4cells, a resistor RCV is provided to each of the voltage measurementlines of each of the 4 terminals CV3 through CV6 in order to protectthose terminals and limit the discharge currents for capacityadjustment. Each of these voltage measurement lines is connected via asensing line LS to a positive electrode or to a negative electrode ofone of the battery cells BC. It should be understood that the GND Sterminals of IC2 and IC3 are connected to the negative electrode of thecorresponding battery cell BC6. For example, when the cell voltage ofthe battery cell BC1 is to be measured, the voltage between theterminals CV1 and CV2 is measured. Furthermore, when the cell voltage ofthe battery cell BC6 is to be measured, the voltage between CV6 and theGND S terminal is measured. In the case of IC1, the cell voltages of itscorresponding battery cells BC1 through BC4 are measured using theterminals CV3 through CV6 and the GND S terminal. Capacitors Cv and Cinfor noise countermeasures are provided between the voltage measurementlines.

In order to utilize the performance of this battery module 9 to themaximum limit, it is necessary to equalize the cell voltages of the 32cells. For example if the variation between the cell voltages is large,then during regenerative charging it is necessary to stop theregenerative charging operation at the time point that battery cellwhose voltage is the highest reaches its upper limit voltage. In thiscase, the regenerative charging operation is stopped irrespective ofwhether or not the cell voltages of the other battery cells have reachedtheir upper limits, and this wastes energy because the brakes then needto be operated. In order to prevent this type of occurrence, undercommand from the microcomputer 30, each of the ICs performs dischargefor adjusting the capacity of its battery cells.

As shown in FIG. 2, to each of IC1 through IC3, balancing switches BS1through BS6 for adjusting the cell capacities are provided between theterminals CV1 and BR1, BR2 and CV3, CV3 and BR3, BR4 and CV5, CV5 andBR5, and BR6 and GND S. For example, if discharge of the battery cellBC1 of IC1 is to be performed, then the balancing switch BS3 is turnedON. When this is done, a balancing current flows along the path from thepositive electrode of the battery cell CV1→the resistor RCV→the terminalCV1→the balancing switch BS3→the terminal BR3→the resistor RB→to thenegative electrode of the battery cell CV1. RB or RBB is a resistor forbalancing.

The communication circuits 602 and 604 described above are providedbetween IC1 through IC3. Communication commands from the microcomputer30 are inputted to the communication circuit 602 via a photo-coupler PH,and are received via the communication circuit 602 at a receptionterminal LIN1 of IC1. And data and a command corresponding to thiscommunication command are transmitted from a transmission terminal LIN2of IC1. The communication command received at the reception terminalLIN1 of IC2 is transmitted from its transmission terminal LIN2.Reception and transmission are performed in order in this manner, andthe transmitted signal is transmitted from the transmission terminalLIN2 of IC3 and is received via a photo-coupler PH at a receptionterminal of the microcomputer 30. According to the communicationcommands that they have received, IC1 through IC3 perform transmissionof measurement data such as cell voltages and so on to the microcomputer30, and also perform balancing operation. Furthermore, each of IC1through IC3 detects cell excessive charge on the basis of the cellvoltages that are measured. The results of this detection (anomalysignals) are transmitted to the microcomputer 30 via the communicationcircuit 604.

FIG. 3 is a figure schematically showing an internal block of one of theICs, and particularly shows the example of IC2 to which the 6 batterycells BC1 through BC6 are connected. It should be understood that theother ICs also have a similar structure, but the explanation iscurtailed. In IC2 there are provided a multiplexer 120 that serves as abattery state detection circuit, an analog to digital converter 122A, anIC control circuit 123, a diagnosis circuit 130, transmission inputcircuits 138 and 142, transmission output circuits 140 and 143, astarting circuit 254, a timer circuit 150, a control signal detectioncircuit 160, a differential amplifier 262, and an OR circuit 288.

The terminal voltages of the battery cells BC1 through BC6 are inputtedto the multiplexer 120 via the terminals CV1 through CV6 and GND S. Themultiplexer 120 selects any of these terminals CV1 through CV6 and GNDS, and inputs the voltage between the terminals to the differentialamplifier 262. The output of this differential amplifier 262 isconverted to a digital value by the analog to digital converter 122A.This voltage between terminals that has been converted to a digitalvalue is sent to the IC control circuit 123, and is retained by aninternal data retention circuit 125. The terminal voltages of thebattery cells BC1 through BC6 that are inputted to the terminals CV1through CV6 and GND S are biased with respect to the ground potential ofIC2 by potentials based upon the terminal voltages of the battery cellsthat are connected in series. The influence of the bias potentialsdescribed above are eliminated by the above described differentialamplifier 262, and analog values based upon the terminal voltages ofeach of the battery cells BC1 through BC6 are inputted to the analog todigital converter 122A.

Along with having a calculation function, the IC control circuit 123includes the data retention circuit 125, a timing control circuit 126that periodically performs voltage measurement and state diagnosis, anda diagnosis flag retention circuit 128 in which a diagnosis flag fromthe diagnosis circuit 130 is set. This IC control circuit 123 decodesthe details of communication commands inputted from the transmissioninput circuit 138, and performs processing corresponding to thesedetails. Such commands may include, for example, commands that requestthe measured values of voltages between terminals of battery cells,commands that request discharge operation for adjusting the states ofcharge of battery cells, commands to start the operation of these ICs(“Wake Up” commands), commands to stop operation (“Sleep” commands),commands that request address setting, and so on.

The diagnosis circuit 130 performs various types of diagnosis on thebasis of the measured values from the IC control circuit 123, forexample excessive charge diagnosis and excessive discharge diagnosis.And the data retention circuit 125 may, for example, include a registercircuit: it stores the voltages of the battery cells BC1 through BC6that are detected between the respective terminals, in correspondencewith these various battery cells BC1 through BC6, and also holds otherdetected values so that they can be read out to addresses that aredetermined in advance.

At least two different power supply voltages VCC and VDD are used in theinternal circuitry of this IC2. In the example shown in FIG. 3, thevoltage VCC is the total voltage of the battery cell group consisting ofthe battery cells BC1 through BC6 that are connected in series, whilethe voltage VDD is generated by a constant voltage power supply 134. Themultiplexer 120 and the transmission input circuits 138 and 142 forsignal transmission operate with the high voltage VCC. Furthermore, theanalog to digital converter 122A, the IC control circuit 123, thediagnosis circuit 130, and the transmission output circuits for signaltransmission operate with the constant voltage VDD.

The signal received at the reception terminal LIN1 of IC2 is inputted tothe transmission input circuit 138, and the signal received at itsreception terminal FFI is inputted to the transmission input circuit142. The transmission input circuit 142 has a similar circuit structureto that of the transmission input circuit 138. The transmission inputcircuit 138 includes a circuit 231 that receives signals from otherneighboring ICs, and a circuit 234 that receives signals from thecircuit 231 and the photo-coupler PH.

As shown in FIG. 2, in the case of IC1 that is the IC at the firststage, it is the signal from the photo-coupler PH that is inputted atits reception terminal LIN1, while in the cases of the other ICs IC2 andIC3, it is the signals from the adjacent ICs that are inputted at theirreception terminals LIN1. Due to this, which of the circuits 231 and 234is the one that is used is selected by the changeover unit 233 on thebasis of the control signal supplied to the control terminal CT of FIG.3. This control signal supplied to the control terminal CT is inputtedto the control signal detection circuit 160, and the changeover unit 233performs its changeover operation according to a command from thecontrol signal detection circuit 160.

In other words, when the direction of transmission of the ICs is to theIC at the first stage, in other words when a signal from the higherlevel controller (i.e. the microcomputer 30) is inputted to thereception terminal LIN1 of that IC, then the changeover unit 233 closesits lower side contact point, so that the output signal of the circuit234 is outputted from the transmission input circuit 138. On the otherhand, when a signal from the adjacent IC is inputted to the receptionterminal LIN1 of this IC, then the changeover unit 233 closes its upperside contact point, so that the output signal of the circuit 232 isoutputted from the transmission input circuit 138. Since, in the case ofIC2 as shown in FIG. 3, the signal from the adjacent IC1 is inputted tothe transmission input circuit 138, accordingly the changeover unit 233closes its upper side contact point. Since the peak value of the outputwaveform that is outputted from the higher level controller (i.e. themicrocomputer 30) and the peak value of the output waveform that isoutputted from the transmission terminal LIN2 of the adjacent IC aredifferent, accordingly the threshold values for decision are different.Due to this, the changeover unit 233 of the circuit 138 comes to bechanged over on the basis of the control signal at the control terminalTC. It should be understood that the communication circuit 604 also hasa similar structure.

The communication command received at the reception terminal LIN1 isinputted to the IC control circuit 123 via the transmission inputcircuit 142. And the IC control circuit 123 outputs data and a commandcorresponding to this communication command that has been received tothe transmission output circuit 140. This data and command aretransmitted from the transmission terminal LIN2 via the transmissionoutput circuit 140. It should be understood that the transmission outputcircuit 143 has a similar structure to that of the transmission outputcircuit 140.

The signal received from the terminal FFI is used for transmitting ananomalous condition (i.e. an excessive charge signal). When a signalthat indicates an anomaly is received from the terminal FFI, this signalis inputted to the transmission output circuit 143 via the transmissioninput circuit 142 and the OR circuit 288, and is outputted from thetransmission output circuit 143 via the terminal FFO. Furthermore, whenan anomaly is detected by the diagnosis circuit 130, without anyrelationship with the contents received at the terminal FFI, a signalthat indicates an anomaly is inputted to the transmission output circuit143 from the diagnosis flag retention circuit 128 via the OR circuit288, and is outputted from the transmission output circuit 143 via theterminal FFO.

When a signal that has been transmitted from the adjacent IC or from thephoto-coupler PH is received by the starting circuit 254, the timercircuit 150 operates, and the voltage VCC is supplied to the constantvoltage power supply 134. Due to this operation, the constant voltagepower supply 134 goes into the operational state, and outputs theconstant voltage VDD. When this constant voltage VDD from the constantvoltage power supply 134 is outputted, the IC2 goes from the sleep stateinto the aroused operational state.

As previously described, the balancing switches BS1 through BS6 areprovided within the IC2 for adjusting the charge amounts of the batterycells BC1 through BC6. In this embodiment, PMOS switches are used forthe balancing switches BS1, BS3, and BS5, while NMOS switches are usedfor the balancing switches BS2, BS4, and BS6.

The opening and closing of these balancing switches BS1 through BS6 iscontrolled by the discharge control circuit 132. On the basis of acommand from the microcomputer 30, a command signal for makingcontinuous the balancing switch that corresponds to a battery cell thatshould be discharged is sent from the IC control circuit 123 to thedischarge control circuit 132. And the IC control circuit 123 receives acommand from the microcomputer 30 by communication that specifies adischarge time period corresponding to each of the battery cells BC1through BC6, and executes the discharge operation described above.

Diagnosis and Measurement: Summary of the Operating Schedule

FIG. 4 is a figure for explanation of the timing of the measurementoperation performed by the timing control circuit 126 shown in FIG. 3.Along with the operation of measurement, each of the ICs shown in FIG. 2is also endowed with a function of performing diagnosis operation, and,while performing measurement repeatedly at a timing as described in FIG.4, also executes diagnosis synchronized with this measurement. It shouldbe understood that while, in FIG. 2 described above, the cell group forIC1 only includes four battery cells, the circuitry of each of IC1through IC3 is capable of handling six battery cells. Accordingly, thenumber of battery cells that can be included in each of the cell groupscan be increased up to a maximum of six. Due to this, in FIG. 4 thatshows the operational timing, it will be supposed that the number ofbattery cells included in the cell group is six.

The number of battery cells making up each of the cell groups to whichIC1 through IC3 are provided is set individually. By doing this, stagesignals are generated corresponding to the number of battery cells ofthe cell groups that correspond to each of IC1 through IC3. By providingthis type of structure, along with it becoming possible to change thenumber of battery cells making up each of the cell groups, so that thefreedom of design is increased, also it becomes possible to performprocessing at high speed.

As mentioned above, FIG. 4 is a figure for explanation of the timing ofthe diagnosis operation and the measurement operation. The timing of theabove described measurement operation, and the measurement cycle and thediagnosis operation, are managed by the starting circuit 254 and by astage counter that consists of a first stage counter 256 and a secondstage counter 258. These stage counters 256 and 258 generate controlsignals (i.e. timing signals) that manage the overall operation of theintegrated circuit. While the stage counters 256 and 258 are notactually separate, they will be described as separate here for theconvenience of explanation. These stage counters could be conventionalcounters, or could be shift registers.

When the starting circuit 254 (1) receives at the reception terminalLIN1 a communication command sent from the transmission path thatrequests “Wake Up”, or (2) the power supply voltage of the IC that issupplied reaches a predetermined voltage, or (3) receives a signal thatindicates that the starter switch of the vehicle (i.e. its key switch)has been turned ON, then it outputs a reset signal to the first andsecond stage counters 256 and 258 so as to put both of these stagecounters 256 and 258 into its initial state, and then outputs a clocksignal of a predetermined frequency. In other words, IC1 executes itsmeasurement and diagnosis operation upon any one of the above conditions(1) through (3). On the other hand, if a communication command has beenreceived from the transmission path that requests “Sleep”, or if it hasnot been possible to receive any such communication command for at leasta predetermined time period, then the starting circuit 254 stops theoutput of the clock at the timing that it returns the stage counters 256and 258 to their reset states, in other words to their initial states.Since the progression of the stages is stopped by this stopping of theoutput of the clock, accordingly the execution of the above describedmeasurement operation and diagnosis operation goes into the stoppedstate.

Upon receipt of the clock signal from the starting circuit 254, thefirst stage counter 256 outputs a count value that controls the timingof processing during each interval of a stage STG2 (i.e. during each ofan interval [RES of STGCal] to an interval [measurement of STGPSBG] thatwill be described hereinafter). The decoder 257 generates a timingsignal STG1 that controls the processing timing within each interval ofthe stage STG2. And, according to the progression of the count value ofthe second stage counter 258, the corresponding interval from the leftto the right of an operation table 260 is changed over in order.According to the count value of the second stage counter 258, a stagesignal STG2 that specifies each interval is outputted from the decoder259.

The first stage counter 256 is a lower level counter, while the secondstage counter 258 is a higher level counter. At the count value “0000”of the second stage counter 258, between “0000” to “1111” of the countvalue of the first stage counter 256, a signal is outputted from thedecoder 259 that indicates the RES interval of the stage STGCal(hereinafter this will be termed the interval [STGCal RES]). Andprocessing of various types performed during this interval [STGCal RES]is executed on the basis of the signal of the decoder 257 that isoutputted on the basis of the count values “0000” through “1111” of thefirst stage counter 256.

It should be understood that although, in FIG. 4, the first stagecounter 256 is described in a simplified manner as being a four bitcounter, if for example this first stage counter 256 is actually aneight bit counter, then it becomes possible to perform processing of 256types, if it is supposed that different processing operations areperformed for each count. For the case of the second stage counter 258as well, just as for the first stage counter 256, it is also possible toperform a large number of different processing operations if it issupposed that a large number of counts are possible.

When the count value of the first stage counter 256 reaches “1111”, thenthe interval [STGCal RES] ends, and the count value of the second stagecounter 258 becomes “0001” and the interval [measurement of STGCal]starts. And, during the interval [measurement of STGCal] while the countvalue of the first stage counter 258 is “0001”, processing of varioustypes is executed on the basis of a signal that is outputted from thedecoder 257 on the basis of the count values “0000” through “1111” ofthe first stage counter 256. And, when the count value of the firststage counter 256 reaches “1111”, then the interval [measurement ofSTGCal] ends, and the count value of the second stage counter 258becomes “0010” and the interval [STGCV1 RES] starts. Similarly in thisinterval [STGCV1 RES], when the count value of the first stage counter256 reaches “1111”, then this interval [STGCV1 RES] ends, and the countvalue of the second stage counter 258 becomes “0011” and the interval[measurement of STGCV1] starts.

In this manner, it starts from the interval [STGCal RES], the operatinginterval shifts rightward in order according to the count of the secondstage counter 258, and the basic operation ends at the end of theinterval [measurement of STGPSBG]. When subsequently the second stagecounter 258 counts up, the interval [STGCal RES] restarts.

It should be understood that, since in the example shown in FIG. 2 onlyfour battery cells are connected to IC1, accordingly the stages STGCV5and STGCV6 in the table 260 are not used, or they are skipped and arenot present. Furthermore, if the contents of the second stage counter258 is forcibly set to some specified count value, then the processingduring the interval that corresponds to this count value may beexecuted.

Diagnosis and Measurement: Diagnosis and Measurement at Each Stage

In the RES interval for each stage, initialization is performed of theanalog to digital converter 122A that is used for measurement. In thisembodiment, an analog to digital converter 122A of a charge/dischargetype in which a capacitor is employed for reducing the influence ofnoise is used, and discharge of electric charge that was accumulated inthe capacitor during the operation that was performed the previous timeand so on is implemented in this RES interval. In the measurementintervals for each stage in the row 260Y2, measurement is executed usingthe analog to digital converter 122A, and diagnosis of the subject thatwas measured is performed on the basis of the value that has beenmeasured.

In the stages STGCV1 through STGCV6, the terminal voltages of thebattery cells are measured in order in the measurement intervals, andmoreover, from the values that are measured, diagnosis is performed asto whether each of the battery cells is in a state of excessive chargeor excessive discharge. The diagnoses of excessive charge and excessivedischarge are set so as to have a certain security breadth, in order toensure that the states of excessive charge or excessive discharge do notactually occur. It should be understood that, if as shown in FIG. 2 thenumber of battery cells connected to the IC is four, then the stagesSTGCV5 and STGCV6 are skipped. In the measurement interval of the stageSTGVDD, the output voltage of the constant voltage power supply 134shown in FIG. 3 is measured. And, in the measurement interval of thestage STGTEM, the output voltage of the temperature sensor is measured.Finally, in the measurement interval of the stage STGPSBG, the referencevoltage is measured.

Diagnosis and Measurement: Measurement of the Terminal Voltages of theBattery Cells

The block diagram shown in FIG. 5 shows the details of a digital circuitportion of the internal blocks of the IC shown in FIG. 3. The signalsSTG1 and STG2 from the decoders 257 and 259 shown in FIG. 4 are inputtedto the multiplexer 120, and selection operation is performed by themultiplexer 120 on the basis of these signals. For example, when thevoltage of the battery cell BC1 is to be measured, and when the terminalCV1 and the terminal CV2 are selected, then the voltage of the batterycell BC1 is outputted from the multiplexer 120 to the differentialamplifier 262. Now, this measurement of the terminal voltage of abattery cell will be explained.

It should be understood that, since the battery cells BC1 through BC4(or BC1 through BC6) are connected in series, the negative electrodepotentials of their terminal voltages are different. Due to this, thedifferential amplifier 262 is used for aligning them to a referencepotential (GND potential in IC1 through IC3). The output of thedifferential amplifier 262 is converted to a digital value by the analogto digital converter 122A, and is outputted to the averaging circuit264. The averaging circuit 264 obtains the average value of apredetermined number of measurement results. In the case of the batterycell BC1, this average value is stored in the register CELL1 of thecurrent value storage circuit 274. It should be understood that thecurrent value storage circuit 274, the initial value storage circuit275, and the reference value storage circuit 278 of FIG. 5 correspond tothe data retention circuit 125 of FIG. 3.

The averaging circuit 264 calculates the average value of the number oftimes of measurement maintained by the averaging control circuit 263,and its output is stored in the current value storage circuit 274described above. If the averaging control circuit 263 just commands “1”,then the output of the analog to digital converter 122A is stored in theregister CELL1 of the current value storage circuit 274 just as it iswithout being averaged. But, if the averaging control circuit 263commands “4”, then the measurement results for the terminal voltage ofthe battery cell BC1 for four times are averaged together, and theaverage value thereof is stored in the register CELL1 of the currentvalue storage circuit 274 described above. In this calculation of theaverage over four times, first it is necessary to perform measurementaccording to the stages of FIG. 4 four times, but from the fourth time,by using the four newest measured values in the calculation, it becomespossible to perform averaging calculation by the averaging circuit 264upon each measurement. By providing the averaging circuit 264 thatperforms averaging a predetermined number of times as described above,it is possible to eliminate the bad influence of noise. The DC power ofthe battery module 9 shown in FIG. 1 is supplied to an inverter device,and is converted into AC power. The operation by the inverter devicewhen performing this conversion from DC power to AC power to gocontinuous and discontinuous for current switching is performed at highspeed, and, while a high amount of noise is generated at this time, byproviding the averaging circuit 264, there is the beneficial effect thatit is possible to reduce the negative influence of this type of noise.

The digital value of the terminal voltage of the battery cell BC1 thathas been digitally converted is stored in the register CELL1 of thecurrent value storage circuit 274. The above described measurementoperation is performed during the measurement interval [measurement ofSTGCV1] of FIG. 4.

Diagnosis of Excessive Charge

Thereafter, during the interval in the stage STGCV1 shown asmeasurement, diagnosis operations are performed on the basis of themeasured value. As these diagnosis operations, excessive chargediagnosis and excessive discharge diagnosis are performed. Beforeentering upon these diagnosis operations, reference values for diagnosisare transmitted from the microcomputer 30 to the various integratedcircuits, and an excessive charge diagnosis reference OC (i.e. anexcessive charge threshold value OC) is registered in the referencevalue storage circuit 278; and, moreover, an excessive dischargediagnosis reference OD (i.e. an excessive discharge threshold value OD)is also registered in the reference value storage circuit 278

On the basis of the outputs of the first stage counter 256 and thesecond stage counter 258 shown in FIG. 4, and according to the selectionsignal created by the decoder 257 and the decoder 259 (the signals STG1and STG2), the digital multiplexer 272 reads out the terminal voltage ofthe battery cell BC1 from the register CELL1 of the current valuestorage circuit 274 and sends it to a digital comparator 270.Furthermore, the digital multiplexer 276 reads out the excessive chargethreshold value OC from the reference value storage circuit 278 andsends it to the digital comparator 270. The digital comparator 270compares together the terminal voltage of the battery cell BC1 from theregister CELL1 and the excessive charge threshold value OC, and, if theterminal voltage of the battery cell BC1 is greater than the excessivecharge threshold value OC, sets a flag [MFflag] in a flag storagecircuit 284 that denotes an anomaly. Furthermore, it also sets a flag[OCflag] that denotes excessive charge. When these flags are set, ananomaly signal (a one-bit signal) is outputted from the terminal FFO ofthe communication circuit 127, and is sent to the microcomputer 30.Actually control should be performed so that this excessive charge statedoes not occur, so that this type of situation almost never takes place.However, this diagnosis is executed repeatedly in order to ensurereliability.

The communication circuit 127 is for performing transmission andreception of communication commands, and includes the above describedtransmission input circuits 138 and 142 and transmission output circuits140 and 143. It should be understood that the transmission input circuit142 and the transmission output circuit 143 are not shown in the figure.Furthermore, the details of reception and transmission registers 302 and332 will be described hereinafter.

Diagnosis of Excessive Discharge

After this excessive charge diagnosis, diagnosis of excessive dischargeis also performed during the measurement interval in the stage STGCV1.The digital multiplexer 272 reads out the terminal voltage of thebattery cell BC1 from the register CELL1 of the current value storagecircuit 274 and sends it to the digital comparator 270. Furthermore, thedigital multiplexer 276 reads out the reference decision value OD forexcessive discharge from the reference value storage circuit 278 andsends it to the digital comparator 270. The digital comparator 270compares together the terminal voltage of the battery cell BC1 from theregister CELL1 and the decision reference value OD for excessivedischarge, and, if the terminal voltage of the battery cell BC1 is lowerthan the excessive discharge threshold value OD, sets the flag [MFflag]in the flag storage circuit 284 that denotes an anomaly. Furthermore, italso sets a flag [ODflag] that denotes excessive discharge. When theseflags are set, an anomaly signal (a one-bit signal) is outputted fromthe terminal FFO, and is sent to the microcomputer 30. In the same wayas in the case of excessive charge, actually control should be performedso that this excessive discharge state does not occur, so that this typeof situation of excessive discharge almost never takes place. However,this diagnosis is executed repeatedly in order to ensure reliability.

The function of the selection circuit 286 can be changed by acommunication command from the microcomputer 30, and it is possibleselectively to change which of the flags are to be included in the flagsthat are outputted from the terminal FFO. For example, it would beacceptable to consider the condition in which only the flag MFflag isset in the flag storage circuit 284 as being an excessive chargeanomaly. In this case, the excessive discharge anomaly diagnosis outputof the digital comparator 270 is not set in the register MFflag, butonly ODflag is set. It would be possible to arrange to determine whetheror not ODflag is outputted from the terminal FFO by a setting conditionfor the selection circuit 286. In this case it is possible to provide alarge number of different types of control, since it is possible tochange the setting condition from the microcomputer 30.

The explanation described above is for measurement and diagnosis relatedto the battery cell BC1 in the stage STGCV1 of FIG. 4. In a similarmanner, in the next stage STGCV2, the multiplexer 120 of FIG. 5 selectsthe terminal voltage of the battery cell BC2, and outputs it to thedifferential amplifier 262. After the output of the differentialamplifier 262 has been converted to a digital value by the analog todigital converter 122A, its average value is calculated by the averagingcircuit 264, and is stored in the register CELL2 of the current valuestorage circuit 274. And the digital comparator 270 compares togetherthe terminal voltage of the battery cell BC2 that has been read out fromthe register CELL2 by the digital multiplexer 272 and the excessivecharge threshold value OC, and then compares together the terminalvoltage of the battery cell BC2 and the decision reference value OD forexcessive discharge (i.e. the excessive discharge threshold value).Decision as to whether an anomalous condition holds is performed by thiscomparison with the excessive charge threshold value OC and by thiscomparison with the excessive discharge threshold value OD, and if ananomalous condition is occurring, then the flag [MFflag] in the flagstorage circuit 284 that denotes an anomaly is set, and the flag[OCflag] or the flag [ODflag] that specifies the cause of the anomaly isset.

In a similar manner to the above, measurement of the terminal voltage ofthe battery cell BC3 and diagnosis of excessive charge or excessivedischarge thereof is performed in the stage STGCV3, and then measurementof the terminal voltage of the battery cell BC4 and diagnosis ofexcessive charge or excessive discharge thereof is performed in thestage STGCV4.

It should be understood that, if the flag MFflag has been set by thediagnosis of any of the items described above, then this flag isoutputted from the one-bit output terminal FFO via the OR circuit 288,and is transmitted to the microcomputer 30.

Diagnosis and Measurement: Storage of the Initial Data

With the system shown in FIG. 1, when the vehicle is in the drivingstopped state and before the driver starts operation, current supplyfrom the battery module 9 to the inverter device is not performed. Sincethe state of charge (SOC) of each of the battery cells is obtainedaccurately when the terminal voltage of each battery cell that ismeasured in the state in which no charge or discharge current flows tothe battery cells is used, accordingly each integrated circuit startsits measurement operation individually on the basis of actuation of thekey switch of the vehicle, or of receipt from the microcomputer 30 of acommunication command 292 such as “Wake Up” or the like. When themeasurement operation and the diagnosis operation for the battery cellsexplained with reference to FIG. 4 is started by each of the integratedcircuits, and measurements for the number of times to be stored by theaveraging control circuit 263 have been performed, then the calculationby the averaging circuit 264 to obtain averages of the measured valuesis performed. The result of this calculation is first stored in thestorage circuit 274. Each of the integrated circuits performs itsmeasurement of all of the battery cells of the cell group to which thisintegrated circuit is related and the calculation of the average valuesof these measurements independently, and the results of thesecalculations are stored in the registers CELL1 through CELL6 of thecurrent value storage circuit 274 of each of the integrated circuits.

In order accurately to ascertain the state of charge (SOC) of each ofthe battery cells, it is desirable to measure the terminal voltage ofeach of the battery cells in the state in which no charge or dischargecurrent is flowing in that battery cell. By each of the integratedcircuits starting the measurement operation individually in the abovemanner, the terminal voltage of each of the battery cells to which eachof the integrated circuits is related is measured before current supplyfrom the battery module 9 to the inverter device, and the results arestored in the registers CELL1 through CELL6 of their current valuestorage circuits 274. Since the measured values that are stored in thecurrent value storage circuits 274 are thereafter overwritten by newmeasurement results, before starting the supply of current, themeasurement results are copied from the registers CELL1 through CELL6 ofthe current value storage circuit 274 to registers BCELL1 through BCELL6of the initial value storage circuit 275, and are thus stored by theinitial value storage circuit 275. Since the measured values beforestarting the supply of current from the battery module 9 to the inverterdevice are stored in the initial value storage circuit 275 in thismanner, accordingly it is possible to defer processing for calculatingthe state of charge (SOC) and so on, and it is possible preferentiallyto execute processing for diagnosis whose priority level is high. Afterthe processing whose priority level is high is executed and supply ofcurrent from the battery module 9 to the inverter device has beenstarted, the state of charge (SOC) of each of the battery cells iscalculated on the basis of the measured values, and it becomes possibleto perform control for adjusting the state of charge (SOC) on the basisof accurate state detection. Sometimes the driver of the vehicle wishesto start driving the vehicle as quickly as possible, so that it isdesirable for it to be made possible to supply current to the inverterdevice quickly, as described above.

At the timing in the example shown in FIG. 5 at which, as describedabove, the measured values are stored in the current value storagecircuit 274 before starting the supply of current to the inverter devicethat constitutes the electrical load, diagnosis by the digitalcomparator 270 of excessive charge or excessive discharge and diagnosisof leakage current and so on can be implemented. Due to this, it ispossible to ascertain the existence of any anomalous condition beforethe supply of DC power to the inverter device. If an anomalous conditionhas occurred, this anomaly can be detected by the above diagnosis beforesupply of current, so that it becomes possible to institutecountermeasures such as non-supply of DC power to the inverter device,or the like. Furthermore since, by copying the values that are initiallymeasured before the supply of current and that are stored in the currentvalue storage circuit 274 to the initial value storage circuit 275, itis possible to keep them stored in the dedicated initial value storagecircuit 275, accordingly there are the outstandingly advantageouseffects of enhancing the security and of ascertaining accurate states ofcharge (SOC).

Communication Commands

FIG. 6 is a figure for explanation of the operation in IC1 for thetransmission and reception of communication commands. The otherintegrated circuits IC2 and IC3 also perform similar operations, asdescribed above. A communication command that is sent from themicrocomputer 30 to the reception terminal LIN1 of IC1 has 5 portions inall, each of which is a single 8-bit unit, thus having a single basicstructure containing 5 bytes. However, in the following explanation,sometimes such a command becomes longer than 5 bytes, and the commandsare not to be considered as being limited to 5 bytes. The communicationcommands are inputted from the reception terminal LIN1 to a receptionregister 322, and are stored therein. It should be understood that thisreception register 322 is a shift register, and the signal that isserially inputted from the reception terminal LIN1 is shifted in orderas it is inputted to the reception register 322, so that the headerportion of this communication command is stored in a break field portion324 that is a header portion of the register, while the subsequentportion is stored sequentially.

As described above, the leading 8 bits of the communication command 292that is stored in the reception register 322 are a break field 324 thatconsists of a signal indicating that a signal has arrived. The second 8bits is a synchronous field 326 that consists of a signal that functionsto establish synchronization. The third 8 bits is a subject address thatspecifies which integrated circuit among IC1 through IC4 is to be thesubject of the command and where it is, and an identifier 328 thatspecifies the details of the command. The fourth 8 bits stores data thatis required for executing this command as data 330 that specifies thedetails of the communication (i.e. the control contents). This portionis not limited to being a single byte. The fifth 8 bits is a checksum332 for checking whether or not an error has occurred during thetransmission and reception operation, and, if it has not been possibleto perform the transmission accurately due to the presence of noise orthe like, then it is possible to detect this fact by using thischecksum. In this manner, the communication command from themicrocomputer 30 consists of five portions: the break field 324, thesynchronous field 326, the identifier 328, the data 330, and thechecksum 312. If each of these consists of a single byte, then thecommunication command consists of 5 bytes, and this 5 byte structure isthe basic structure; but the data 330 is not limited to being a singlebyte, and, accordingly to requirements, sometimes it may be increased toa greater data length.

The synchronous field 326 is used for establishing synchronizationbetween a transmission clock on the transmitting side and a receptionclock on the reception side. The timing at which the pulses of thesynchronous field 326 are sent and arrive is detected by a synchronizingcircuit 342, and synchronization of this synchronizing circuit 342 isperformed by the timing of the pulses of the synchronous field 326. Thereception register 322 receives this continuous signal at this matchedtiming. By doing this, the beneficial effect is obtained that it ispossible accurately to select the comparison timing between the signalthat is arriving and the threshold value at which the true value of thesignal is determined, so that it is possible to reduce errors during thetransmission and reception operation.

The communication command 292 is sent from the microcomputer 30 via thecommunication circuit 602 shown in FIG. 2 to the reception terminal LINof IC1 that is the IC at the first stage, and is then sent from thetransmission terminal LIN2 of this IC1 to the reception terminal LIN1 ofthe next IC2, and moreover is sent from the transmission terminal LIN2of IC2 to the reception terminal LIN1 of IC3 that is the IC at the laststage, and then is sent from the transmission terminal LIN2 of this IC3to a reception terminal LIN1 (not shown in the figures) of themicrocomputer 30. In this manner, the communication command 292 istransmitted via the communication circuit 602 in which the transmissionand reception terminals of the integrated circuits IC1 through IC3 areconnected in series in the form of a loop. A similar situation holds inrelation to IC4 through IC6 of the battery block 9B.

While the circuitry of IC1 has been explained as being representative ofall of the integrated circuits, as described above, the other integratedcircuits also have the same structure and operation. The communicationcommand 292 is transmitted to the reception terminal LIN1 of IC1. Andthe communication command 292 that has been received by each of theintegrated circuits is transmitted from its transmission terminal LIN2to the next integrated circuit. In the operation described above, it isdecided by the command processing circuit 344 of FIG. 6 whether or notit is itself the designated subject of a communication command 292 thatit has received, and, if this integrated circuit is itself the subject,then it performs processing on the basis of the communication command.The processing described above is performed sequentially on the basis oftransmission and reception of communication commands 292 by each of theintegrated circuits.

Accordingly, even if a communication command that is stored in thereception register 322 has no relationship with IC1, it is stillnecessary to perform transmission to the next integrated circuit on thebasis of this communication command 292 that has been received. Thus,the command processing circuit 344 inputs the contents of the identifier328 of a communication command 292 that has been received, and decideswhether or not this IC1 is itself the command subject of thiscommunication command 292. And, if IC1 is not itself the command subjectof this communication command 292, then it transfers the contents of theidentifier 328 and of the data 330 just as it is to the identifier 308and data 310 portions of the transmission register 302. Moreover, thecircuit 344 inputs the checksum 312 for checking upon erroneoustransmission and reception operation and completes the signal fortransmission in the transmission register 302, and then transmits thissignal from the transmission terminal LIN2. In a similar way to thereception register 322, the transmission register 302 is also built as ashift register.

If the subject of the communication command that has been received isitself, then one or more commands are executed on the basis of thecommunication command 292. This execution will now be explained in thefollowing.

Sometimes it is the case that the subject of the communication command292 that has been received is related to all of the integrated circuitsas a whole, including this IC. For example, this type of commandincludes the RES command, the “Wake Up” command, and the “Sleep”command. When a RES command is received, the details of this command aredecoded by the command processing circuit 344, and a RES signal isoutputted. When this RES signal is generated, all the data stored ineach of the current value storage circuit 274, the initial value storagecircuit 295, and the flag storage circuit 284 of FIG. 5 is set to “zero”as initial value. While in this case the contents of the reference valuestorage circuit 278 of FIG. 5 does not become “zero” it would also beacceptable to arrange for it to be set to “zero”. If the contents of thereference value storage circuit 278 is changed to “zero”, then, sincethe measurement and diagnosis shown in FIG. 4 are executed individuallyby each of the integrated circuits after generation of the RES signal,accordingly it becomes necessary to set the values in the referencevalue storage circuit 278 that will become the reference values fordiagnosis rather rapidly. The reference value storage circuit 278 ismade as a circuit whose contents are not changed by the RES signal inorder to avoid this inconvenience. Since the values in the referencevalue storage circuit 278 is not attribute data that changes frequently,accordingly it would also be acceptable to utilize the previous values.If there is a requirement for these values to be changed, then they maybe changed individually with other communication commands 292. Thevalues stored in the averaging control circuit 263 by the RES signal area predetermined number of values, for example 16. In other words, if notchanged by some communication command 292, a setting is established forthe average of 16 measured values to be calculated.

When a “Wake Up” command is outputted from the command processingcircuit 344, the starting circuit 254 of FIG. 4 starts its operation,and its operations of measurement and diagnosis are started. Due tothis, the power consumed by this integrated circuit itself is increased.On the other hand, when a “Sleep” signal is outputted from the commandprocessing circuit 344, the operation of the starting circuit 254 ofFIG. 4 is stopped, and its operations of measurement and diagnosis arestopped. Due to this, the power consumed by this integrated circuititself is remarkably reduced.

Next, the reading in and changing of data according to a communicationcommand 292 will be explained with reference to FIG. 6. The identifier328 of the communication command 292 designates the integrated circuitthat is to be selected. In the case of a data write command to theaddress register 348 or to the reference values storage circuit 278, orof a data write command to the averaging control circuit 263 or to theselection circuit 286, the command processing circuit 344 designates thesubject for the data 330 to be written into on the basis of the detailsof the command, and writes the data 330 into this register that is thesubject for being written into.

The address register 348 is a register in which the address of thisintegrated circuit itself is stored, and its own address is determinedaccording to these contents. By setting the contents of this addressregister 348 to zero upon the RES signal, the address of this integratedcircuit itself becomes the address “zero”. And, when the contents ofthis address register 348 is changed by a new command, the address ofthis integrated circuit itself is changed to these changed contents.

Apart from the stored contents in the address register 348 being changedby the communication command 292, the stored contents in the referencevalue storage circuit 278, the flag storage circuit 284, the averagingcontrol circuit 263, and the selection circuit 286 described in FIG. 5may also be changed. If a subject of change related to these isdesignated, then the contents of the data 330, that is the changedvalue, is sent to the circuit that is the subject of change via a databus 294, so that its stored contents are changed. The circuit of FIG. 5then executes its operation on the basis of these contents that havebeen changed.

A transmission command for data that is being stored internally to theintegrated circuit is included in the communication commands 292.Designation of the data that is to be the subject of transmission isperformed by a command with the identifier 328. For example, when aninternal register to the current value storage circuit 274 or thereference value storage circuit 278 is designated, then the contentsstored in the designated register is stored in the data 310 circuit ofthe transmission register 302 via the data bus 294, and is transmittedas the requested data contents. In this manner, it becomes possible forthe microcomputer 30 shown in FIG. 1 to input, using communicationcommands 292, the needed values measured by the integrated circuits andthe flags that designate their states.

The First Embodiment

As described above, when performing cell voltage measurement, from amongthe terminals CV1 through CV6 and the GNDS terminal, a pair of terminalsthat are connected to both of the electrodes of the battery cell that isto be the subject of measurement are selected by the multiplexer 120shown in FIG. 3. A selection signal for this terminal selection isgenerated by a digital region within IC2 (the IC control circuit 123 ofFIG. 3), and is inputted to the multiplexer 120. However, if amalfunction occurs in the multiplexer 120, then sometimes it may happenthat different terminals from those in the command containing theselection signal are selected. In this type of case as well, in theprior art, from the cell voltage transmitted to the side of themicrocomputer 30, it was not possible to determine whether or not thecell voltage that was measured had been correctly selected. Accordingly,as explained below, in this first embodiment it is arranged for it to bepossible to decide whether or not the selection of terminals by themultiplexer 120 has been correctly performed, on the basis of the cellvoltage that has been transmitted to the side of the microcomputer 30.

In the following, this multiplexer connection diagnosis will beexplained with reference to FIGS. 7A through 12. As described above,each of the ICs, along with performing voltage measurement and statediagnosis periodically on the basis of commands by the timing controlcircuit 126 with no relationship with commands from the microcomputer 30that is the higher level controller, also turns the balancing switchesON on the basis of commands from the microcomputer 30, and therebyperforms adjustment of the capacities of the battery cells. However, inthe state in which capacity adjustment is being performed by turning oneor more of the balancing switches to ON, due to the flow of dischargecurrent, voltage drop takes place in the corresponding resistors RCVthat are provided in the voltage measurement lines for the terminals VC1through VC6, so that the voltages between the terminals VC come to bedifferent from the voltage values of the battery cells. Due to this abalancing switch masking function (hereinafter termed the “maskfunction”) is provided, according to which, even during the balancingoperation, the balancing switch that gives influence to the measurementis automatically turned to OFF during intervals for measurement of thecell voltages, since otherwise they would exert an influence upon themeasurement of the cell voltages.

Referring to FIGS. 7A and 7B, this mask function will be explained forthe example in which adjustment of the battery cell BC1 is performed byIC2. FIG. 7A is a figure showing IC2, the battery cells BC1 through BC6,and peripheral circuitry for detecting the cell voltages. And FIG. 7B isa figure for explanation of the operation of the balancing switch BS1and the voltage between the terminals CV1 and CV2, when the maskfunction goes ON and OFF. The left side portion of the timing chartshown in FIG. 7B (i.e. a range that shows the mask function ON) showsthe situation when the mask function has been turned ON, and the rightside portion of this timing chart (i.e. a range that shows the maskfunction OFF) shows the situation when the mask function has been turnedOFF.

As previously described, without any relationship with commands from themicrocomputer 30, IC2 performs measurement of the cell voltages of thebattery cells BC1 through BC6 upon a predetermined cycle, and alsoperforms correlated internal diagnosis (for example, excessive chargedetection). And, each time the cell voltages are measured, the cellvoltages that are being retained in the data retention circuit 125 ofFIG. 3 (i.e. the current value storage circuit 274 of FIG. 5) arerewritten. When balancing of the battery cell BC1 is to be performed, acommand to turn the balancing switch BS1 is transmitted to IC2 from themicrocomputer 30. And, according to this command, IC2 turns thebalancing switch BS1 to ON.

When the balancing switch BS1 is turned ON, a discharge current flowsfrom the battery cell BC1 as shown by the arrow sign in FIG. 7A. At thistime, since this discharge current flows in the resistor RCV that isprovided in the voltage measurement line of the terminal CV1,accordingly the voltage between the terminals CV1 and CV2 is reducedfrom the cell voltage Vc1 of the battery cell BC1 by just the voltagedrop ΔV in this resistor RCV. However, the voltages between the otherterminals (CV2 and CV3, CV3 and CV4, CV4 and CV5, CV5 and CV6, and CV6and GND S) do not receive any influence from this discharge current, sothat they reflect the cell voltages Vc2 through Vc6 of the battery cellsBC2 through BC6.

Due to this, in the prior art, during the measurement interval, it hasbeen practiced to provide a function of turning the balancing switchthat is experiencing an influence due to this measurement to the OFFstate, in other words a mask function. In the case of the example shownin FIG. 7A, it is arranged to turn the balancing switch BS1 to OFFduring the voltage measurement interval for the battery cell BC1, asshown in the left half portion of FIG. 7B (that shows the mask functionON state).

Now, when measurement of the voltages of the battery cells BC1 throughBC6 is performed with the mask function turned OFF, the voltage betweenthe terminals CV1 and CV2 experiences the influence of the dischargecurrent, as described above, and becomes Vc1−ΔV. In other words, whenthe mask function is ON, Vc1, Vc2, Vc3, Vc4, Vc5, and Vc6 are measuredin order as being the cell voltages of the battery cells BC1 throughBC6; while, when as shown in the right side portion of FIG. 7B the maskfunction is OFF, the voltages between the terminals become: “voltagebetween CV1 and CV2=Vc1−ΔV”, “voltage between CV2 and CV3=Vc2”, “voltagebetween CV3 and CV4=Vc3”, “voltage between CV4 and CV5=Vc4”, “voltagebetween CV5 and CV6=Vc5”, and “voltage between CV6 and GND S=Vc6”. Inother words, Vc1−ΔV, Vc2, Vc3, Vc4, Vc5, and Vc6 are measured in orderas being the cell voltages of the battery cells BC1 through BC6.

Accordingly, if during measurement of the cell voltage of the batterycell BC1 the multiplexer 120 selects the terminals VC1 and VC2, when themask function is OFF, a voltage is measured that is just ΔV lower thanwhen the mask function is ON. Due to this fact, by comparing togetherthe cell voltage when the mask function is ON and the cell voltage whenthe mask function is OFF, it is possible to diagnose whether or not theterminals VC1 and VC2 have been selected according to command from themultiplexer 120. If the resistance values of the resistors RCV and RBare Rcv and Rb, and the ON resistance of the balancing switch BS1 isRon, then:

ΔV=Vc1·Rcv/(Rb+Rcv+Ron)

By making a decision by comparing the difference Vc1−(Vc1−ΔV)=ΔV againstan appropriate threshold value, it is possible to diagnose whether ornot the battery cell BC1 was correctly selected by the multiplexer 120.

It should be understood that, when BS1 is ON with BS2 through BS6 beingOFF, since the voltage between the other terminals does not change whenthe mask function goes ON and OFF, accordingly it is not possible toperform connection diagnosis of the multiplexer 120 for these otherterminals at this time. For example, if the cell voltages of the batterycells BC2 through BC6 are equal, it is not possible to decide whichterminals are being selected according to commands from the multiplexer120.

FIGS. 8A and 8B are figures for explanation of the diagnosis of terminalselection by the multiplexer 120 during measurement of the cell voltageof the battery cell BC2. First, the balancing switch BS2 is turned ON inthe state with the mask function ON, as shown in FIG. 8B, and the cellvoltage of each of the battery cells is measured. When the balancingswitch BS2 is turned ON, as shown in FIG. 8A, since a discharge currentflows in the resistor RCV that is provided in the voltage measurementline of the terminal CV3, the voltage drop in this resistor RCV exertsan influence both upon the measurement of the voltage between theterminals CV2 and CV3, and also upon the measurement of the voltagebetween the terminals CV3 and CV4. Due to this, in the mask function ONstate, the balancing switch BS2 is turned to OFF during the intervals inwhich the cell voltage of the battery cell BC2 and the cell voltage ofthe battery cell BC3 are measured. As a result, in order, VC1, Vc2, Vc3,Vc4, Vc5, and Vc6 are measured as the respective cell voltages of thebattery cells BC1 through BC6.

Next, when the mask function is turned OFF and the voltages between thevarious terminals are measured, since as shown in FIG. 8A a voltage dropof ΔV is present across the resistor RCV, accordingly the results“voltage between CV1 and CV2=Vc1”, “voltage between CV2 and CV3=Vc2−ΔV”,“voltage between CV3 and CV4=Vc3+ΔV”, “voltage between CV4 and CV5=Vc4”,“voltage between CV5 and CV6=Vc5”, and “voltage between CV6 and GNDS=Vc6” are obtained. In other words, since the cell voltages of thebattery cells BC2 and BC3 are different when the mask function is ON andwhen it is OFF, accordingly, by comparing this difference against anappropriate threshold value, it is possible to diagnose whether or notthe battery cells BC2 and BC3 were correctly selected according tocommand by the multiplexer 120. At this time, ΔV is given byΔV=Vc2·Rcv/(Rb+Rcv+Ron).

In a similar manner, when as shown in FIG. 9A the balancing switch BS3is turned ON with the mask function OFF, the voltages between terminalsbecome “voltage between CV1 and CV2=Vc1”, “voltage between CV2 andCV3=Vc2+ΔV”, “voltage between CV3 and CV4=Vc3−ΔV”, “voltage between CV4and CV5=Vc4”, “voltage between CV5 and CV6=Vc5”, and “voltage betweenCV6 and GND S=Vc6”. Accordingly, it is possible to perform multiplexerconnection diagnosis in relation to the battery cells BC2 and BC3. Atthis time, ΔV is given by ΔV=Vc3·Rcv/(Rb+Rcv+Ron).

FIG. 9B shows the case in which the balancing switch BS4 is turned ONwith the mask function OFF. In this case, the voltages between terminalsbecome “voltage between CV1 and CV2=Vc1”, “voltage between CV2 andCV3=Vc2+ΔV”, “voltage between CV3 and CV4=Vc3”, “voltage between CV4 andCV5=Vc4−ΔV”, “voltage between CV5 and CV6=Vc5+ΔV”, and “voltage betweenCV6 and GND S=Vc6”. At this time, ΔV is given byΔV=Vc4·Rcv/(Rb+Rcv+Ron).

Moreover, FIG. 10A shows a case in which the balancing switch BS5 isturned ON with the mask function OFF. In this case, the voltages betweenterminals become “voltage between CV1 and CV2=Vc1”, “voltage between CV2and CV3=Vc2+ΔV”, “voltage between CV3 and CV4=Vc3”, “voltage between CV4and CV5=Vc4+ΔV”, “voltage between CV5 and CV6=Vc5−ΔV”, and “voltagebetween CV6 and GND S=Vc6”. At this time, ΔV is given byΔV=Vc5·Rcv/(Rb+Rcv+Ron). In either of the cases shown in FIG. 9B andFIG. 10A, it is possible to perform multiplexer connection diagnosis inrelation to the battery cells BC4 and BC5.

Now, the cell voltages of the battery cells BC1 through BC6 are notprecisely constant, but rather do vary somewhat. Due to this, in orderto perform the diagnosis by comparing together the difference and ΔV, itis necessary to set the resistance values of the resistors RCV so thatΔV=Vcj·Rcv/(Rb+Rcv+Ron), for j=1-5, becomes greater than the variationsbetween the cell voltages. Furthermore, in this embodiment, a structureis provided that performs capacity adjustment so that, when thebalancing switches BS1 through BS6 are turned ON and OFF, the variationsof the cell voltages are kept within a predetermined voltage range. Dueto this, the actual variation of voltage becomes less than or equal to avoltage variation threshold value at which capacity adjustment isstarted. Thus, it would also be acceptable to set the values of theresistances of the resistors RCV so that ΔV becomes greater than thevoltage variation threshold value.

Furthermore, if the decision threshold value when performing diagnosisaccording to the differential as described above is not also made to begreater than the variation of cell voltage, then it is not possible toperform accurate diagnosis.

As described above, the value of ΔV depends upon the cell voltages ofthe battery cells BC at which balancing is performed. When implementingmultiplexer connection diagnosis, it would also be acceptable tocalculate ΔV on the basis of the cell voltages that are acquired in astep S11 that will be described hereinafter, and to set the thresholdvalue using this ΔV that has been thus calculated. For example, a valueof 80% of the ΔV that has been calculated may be set as the thresholdvalue. Furthermore, it would also be acceptable to calculate ΔV usingthe average cell voltage, and to set the threshold value using this ΔV.If ΔV is greater than or equal to the threshold value, then it isdecided that the selection by the multiplexer 120 has proceedednormally.

FIG. 10B shows the case in which the balancing switch BS6 is turned ONwith the mask function OFF. In this case, since no resistor RCV ispresent in the path of the discharge current, accordingly the voltagesbetween the terminals are the same as when the mask function is ON. Dueto this, for this diagnosis result only, it is not possible to diagnosewhether or not the terminal selection by the multiplexer 210 in relationto the battery cell BC6 is correct; but it becomes possible to performdiagnosis in this case as well by referring to the cell voltage for thebattery cell BC6 when the other balancing switches BS1 through BS5 wereturned ON, as shown in FIGS. 7A, 8A, 9A, 9B, and 10A.

The reason why is that if, during the cell voltage measurement commandfor the battery cell BC6, the situation arises that some other terminalor terminals are selected, then it is considered that the same type ofmistaken selection would have occurred as well during the diagnoses ofFIGS. 7A, 8A, 9A, 9B, and 10A. Due to this, during the diagnosis of oneof FIGS. 7A, 8A, 9A, 9B, and 10A, some value other than Vc6 would havebeen measured as the cell voltage of the battery cell BC6. Accordinglyif, in all the diagnoses of FIGS. 7A, 8A, 9A, 9B, and 10A, the measuredcell voltage value for the battery cell BC6 was Vc6, then it is possibleto diagnose that the multiplexer 120 did indeed select the battery cellBC6 properly, according to the command that it received.

FIG. 11 is a flow chart showing an example of the above multiplexerconnection diagnosis. The processing for this multiplexer connectiondiagnosis is performed when the vehicle is stopped, in other wordsduring shutdown processing by the microcomputer 30 when the key switchis turned OFF. In a first step S10, the microcomputer 30 acquires viathe CAN information related to the relay state of the batterydisconnector unit BDU (refer to FIG. 1), and makes a decision as towhether or not the relays RL and RLp are open. And if it is decided thatthe relays RL and RLp are in the open state, then the flow of control istransferred to a step S11.

In this step S11, the microcomputer 30 commands IC1 to transmit the cellvoltage data of each battery cell. As a result, IC1 transmits the cellvoltage of each battery cell that is stored in the data retentioncircuit 125 (refer to FIG. 3) from its transmission terminal LIN2. Itshould be understood that, since as shown in FIG. 7B the mask functionis ON in the initial state, accordingly here the cell voltages aremeasured while the mask function is ON, and these voltages aretransmitted to the microcomputer 30.

Next the microcomputer 30 transmits to IC1 a command to turn thebalancing switch BS1 ON in a step S12, and a command to turn the maskfunction OFF in a step S13. Upon receipt of these commands, IC1 turnsthe balancing switch BS1 to ON and then turns the mask function OFF.During this process, IC1 continues to repeat the measurement of cellvoltage and internal diagnosis at a predetermined period Ti, as shown inFIG. 7B.

And, after having issued the mask function OFF command in the step S13,when a predetermined time period has elapsed, in a step S14 themicrocomputer 30 transmits to IC1 a command to transmit the cell voltagedata for the battery cells BC1 through BC6. Here, the predetermined timeperiod is set to be greater than or equal to the time from when IC1turns the mask function to OFF in which at least one measurement cyclefor the cell voltages can be completed; for example this period may beset to twice the length of the measurement cycle Ti internal to the IC.Then in a step S15, along with the mask function of IC1 being turned toON, the balancing switch BS1 is turned to OFF.

Then in a step S16, by comparing the difference between the cell voltageof the battery cell BC1 of IC1 with the mask function ON and the cellvoltage of the battery cell BC1 with the mask function OFF against apredetermined threshold value, a diagnosis is made as to whether or notthe cell battery BC1 is actually being selected by the multiplexer 120,as commanded. And in the next step S17 a decision is made as to whetheror not this multiplexer connection diagnosis has been completed for allof the battery cells. Since, in the example shown in FIG. 1, thecommunication circuit 602 related to transmission of the cell voltagedata and so on are independent for IC1 through IC3 and for IC4 throughIC6, it is possible for transmission of cell voltage data to themicrocomputer 30 to be performed in parallel. If this type of parallelprocessing is performed, then, in the step S17, a decision is made as towhether or not diagnosis related to all 16 of the battery cells has beencompleted.

When multiplexer connection diagnosis related to the terminal selectionof CV1 and CV2 of IC1 has been completed as described above, then theflow of control returns to the step S11 and the next balancing switchBS2 is turned ON. And the processing of the steps S11 through S16 isperformed with the voltage between the terminals CV2 and CV3 selected,and then again with the voltage between the terminals CV3 and CV4selected, so that thereby multiplexer connection diagnosis is performedin relation to the selection of the battery cells BC2 and BC3. This typeof processing is performed in relation to each of the 16 battery cellsconnected to IC1 through IC3 in order, and, when the multiplexerconnection diagnosis in relation to the battery cell BC6 of IC3 has beencompleted, a YES decision is reached in the step S17, and then thismultiplexer connection diagnosis processing terminates.

As described above, in this embodiment, by measuring the cell voltage inthe state with the balancing switch set to ON and with the mask functionset to OFF, and by detecting the difference (ΔV) against the cellvoltage measured with the mask function ON, it is possible to diagnosewhether or not cell selection was actually properly performed by themultiplexer 120 according to the command that it received. And, if ΔV isgreater than or equal to the predetermined threshold value, then it isdiagnosed that the selection operation by the multiplexer 120 functionednormally, whereas if ΔV is less than the predetermined threshold value,then it is diagnosed that an anomaly occurred with the selectionoperation.

Since the diagnosis for detection of the voltage change (ΔV) of themeasured cell voltage that is performed in this manner becomes difficultwhen noise (such as inverter noise or the like) is superimposed upon thecell voltage, and when the amplitude of this noise is equal to orgreater than the anticipated voltage change (ΔV), accordingly this canbecome a cause of erroneous diagnosis. Due to this, in the embodimentdescribed above, it is arranged to perform the multiplexer connectiondiagnosis described above during shutdown processing when the key switchof the vehicle has been turned to OFF and the BDU of FIG. 1 has gone toopen. Furthermore, it would also be acceptable to arrange for themultiplexer connection diagnosis described above to be performed whenthe vehicle is being started (i.e. when the key switch has been turnedto ON), again with the BDU in the open state.

It should be understood that it would also be acceptable to perform themultiplexer connection diagnosis described above while the vehicle isoperating, if it is possible to ensure that the level of noise issufficiently low, and if it is possible to guarantee that the change ofcell voltage due to charge/discharge current is lower than ΔV by asufficient level. For example, this diagnosis may be performed while thevehicle is idling (i.e. when the current is zero). Furthermore, bymeasuring at a speed that is higher than that of the superimposed noise,it is possible to reduce the influence of that noise.

Now sometimes it happens that, even in the state during shutdown afterthe relays have gone to open, polarization of the battery cells due tothe influence of the current that was flowing directly before has notdisappeared, so that the cell voltage is not stable. In this type ofcase, it is desirable to delay the start of the diagnosis processinguntil the cell voltage has become stabilized, and only to start thediagnosis then. An example of this type of processing is shown in FIG.12. In the flow chart shown in FIG. 12, the flow chart shown in FIG. 11is supplemented by the addition of the processing of steps S20 throughS23.

When in the step S10 it is decided that the relays are open, the flow ofcontrol proceeds to a step S20, in which a command that requests thecell voltage of the battery cell BC1 of IC1 is transmitted. Thus thecell voltage Vc1 of the battery cell BC1 is transmitted from IC1 to themicrocomputer 30. It should be understood that while, here, it is shownthat the cell voltage of the battery cell BC1 of IC1 is requested, itcould be the cell voltage of any of the cells. Next in a step S21 thecell voltage acquired in the step S20 and the cell voltage that isstored in the memory of the microcomputer 30 are compared together, andif the difference between them is less than or equal to a predeterminedvalue then the flow of control is transferred to a step S11 and themultiplexer connection diagnosis processing described above isperformed.

It should be understood that, since no cell voltage is stored in thememory when the step S21 is first executed (this is the cell voltagethat was acquired when step S20 was executed the previous time),accordingly, after having stored the cell voltage acquired in the stepS20 in the memory, the flow of control proceeds from the step S21 to astep S22. In this step S22, a decision is made as to whether or not thenumber of times that the processing of the step S21 has been performedhas reached a predetermined number of times. And, if in this step S22 itis decided that the predetermined number of times has not yet beenreached, then the flow of control returns to the step S20.

Until the number of times that the processing of the step S21 has beenperformed reaches the predetermined number of times, a NO decision isreached in the step S22, and the processing of the steps S20→S21→S22→S20is repeated for a predetermined time period. Due to this, the cellvoltage is acquired at predetermined time intervals. The above describedpredetermined value and predetermined time period are set on the basisof the elapsed time from cell voltage acquisition when the mask functionis ON to cell voltage acquisition when the mask function is OFF, and thethreshold value when detecting ΔV. For example, if the predeterminedtime period is equal to the elapsed time, then the predetermined valuemay be set equal to the threshold value; while, if the predeterminedtime period is equal to the elapsed time/10, then the predeterminedvalue may also be set to 1/10 of the threshold value.

In other words, if in the step S21 it is determined that the change isless than or equal to the predetermined value, then the cell voltage hasbecome stabilized to a degree at which it is possible to detect ΔV, andaccordingly the flow of control proceeds to the step S11 and themultiplexer connection diagnosis processing described above is executed.

On the other hand, if the change of the cell voltage is greater than thepredetermined value so that diagnosis cannot be performed, then the flowof control proceeds to the step S22, in which the decision is made as towhether or not the number of times that the processing of the step S21has been performed has reached the predetermined number of times. And,if it is determined in this step S22 that the number of times has beenreached, then the flow of control proceeds to a step S23, in which thefact that the multiplexer connection diagnosis has not been performed isstored as data in the EEPROM, since there is a danger of occurring anerroneous diagnosis.

In this manner, if the number of key cycles, in which it has not beenpossible to perform diagnosis because the polarization has notdisappeared, has continued for a certain number of times in successiondetermined in advance (for example, three times), then the next time(the fourth time), it is arranged to repeat the processing of “the stepsS20→S21→S22→S20” shown in FIG. 12 until the polarization hasdisappeared, and thus to perform multiplexer connection diagnosis onlyafter it has been confirmed that the voltage change has dropped belowthe predetermined value. Due to this, it is possible to avoidmultiplexer connection diagnosis remaining un-implemented over the longterm. Furthermore, if during shutdown processing there is some otherprocessing that can be performed before performing the multiplexerconnection diagnosis, then it would also be acceptable to perform thisprocessing first, so as to allow a longer time period for thepolarization to disappear. It should be understood that if some otherfault such as a fault in the IC itself or a breakage of one of thesending lines SL or the like is detected, then the above multiplexerconnection diagnosis may be omitted.

It should be understood that while, in the embodiment described above,it is arranged to transmit cell voltage data to the microcomputer 30 forall of the battery cells connected to the IC that is the subject fordiagnosis, it would also be acceptable to transmit only the cell voltageof that cell or cells for which diagnosis is required.

The Second Embodiment

In the second embodiment explained below, it is arranged to provide afunction of diagnosing whether or not the battery state detectioncircuit is operating normally, in other words a function of diagnosingwhether or not selection by the multiplexer is being performed normally,and also newly to add a function of diagnosing whether or not anexcessive charge detection circuit (an excessive charge detectionsystem) that detects excessive charge is operating normally.

Multiplexer Selection Diagnosis

FIG. 13 is a figure for explanation of this second embodiment, and showsblocks internal to the integrated circuits (IC1 through IC6), in asimilar way to the case in FIG. 5. To IC1 shown in FIG. 13, in additionto the structure shown in FIG. 5, there are further providedmultiplexers MUX1 through MUX5, resistors RPU, R1 through R4, and RPD,and a switch SW. It should be understood that only structures within thestructure shown in FIG. 5 that are necessary for explanation of thissecond embodiment are shown in FIG. 13. Multiplexers HVMUX1 and HVMUX2are provided to the multiplexer 120, and the outputs of these twomultiplexers HVMUX1 and HVMUX2 are inputted to the differentialamplifier 262. A voltage source 400 internal to IC1 is one that has beenprovided in the prior art; for example, a voltage source or the likethat supplies the reference voltage of an analog to digital converter122A may be used. It should be understood that, instead of a voltagesource, a current source may be used. Furthermore, in FIG. 13, thecommunication circuit 127 of FIG. 5 and a logic circuit are combined,and are provided as a logic/communication circuit 401.

The resistors RPU, R1 through R4, and RPD are connected in series, andthe free end of the resistor RPD is connected to the terminal GND ofIC1, while the free end of the resistor RPU is connected to the switchSW. It should be understood that the terminals V1 through V4 and GND ofFIG. 13 correspond to the terminals CV3 through CV6 and GND S of FIG. 2.The resistance values of the resistors R1 through R4 are set so as allto be different from one another; i.e. so that R1≠R2≠R3≠R4. Due to this,when the switch SW is turned to ON, the voltage of the voltage source400 is divided by the resistors RPU, R1 through R4, and RPD, and thevoltages Vr1, Vr2, Vr3, and Vr4 generated by the resistors R1 through R4are all different from one another. Furthermore, the resistance valuesof the resistors R1 through R4 are set so that the voltages Vr1, Vr2,Vr3, and Vr4 that are generated become values that are outside thenormal range of the cell voltages. In other words, if the normal rangeof the cell voltages is “VcL ≦cell voltage ≦VcU”, then the resistancevalues of the resistors R1 through R4 are set so that the voltages Vr1through Vr4 become either smaller than VcL or larger than VcU.

It should be understood that the resistors RPU and RPD and themultiplexers MUX1 and MUX5 are ones that are provided in order togenerate desired voltages, and are not essential to the structure.Whether or not these are provided is determined according to the voltagesource (or current source) 400, according to the cell voltages, andaccording to the input range of the differential amplifier 262.

While here it is supposed that fixed resistors are used as the resistorsR1 through R4, it would also be possible, for example, to provide themas variable resistors whose resistance values can be changed from theexterior, so that they have resistance values such that voltages aregenerated having significant differences from the cell voltages thathave been read directly previously. For example, if the normal cellvoltage is 3.5 V, then, when the diagnosis mode is started, the resistorR1 may be adjusted so as to yield a cell voltage of 2.5 V, that isoutside the normal cell voltage range.

Each of the multiplexers MUX1 through MUX5 has two input terminalsdesignated as 0 and 1, and it is possible to select either one of theseinput terminals 0 and 1. The input terminal 0 of the multiplexer MUX1 isconnected to the positive electrode side of the battery cell BC1 via theinput terminal V1 of IC1 and the sensing line L1, while its inputterminal 1 is connected between the resistor RPU and the resistor R1. Onthe other hand, the output side of this multiplexer MUX1 is connected toan input terminal 00 of the multiplexer HVMUX1.

When the multiplexer MUX1 selects its input terminal 0, the potential atthe input terminal 00 of the multiplexer HVMUX1 becomes the samepotential as that of the positive electrode side of the battery cellBC1; and, conversely, when the multiplexer MUX1 selects its inputterminal 1, the potential at the input terminal 00 of the multiplexerHVMUX1 becomes the potential between the resistor RPU and the resistorR1. In other words, by changing over the multiplexer MUX1, it ispossible to input an already known voltage that is determined in advanceto the input terminal 00 of the multiplexer HVMUX1, instead of the cellvoltage.

And the input terminal 0 of the multiplexer MUX2 is connected to thepositive electrode side of the battery cell BC2 (i.e. the negativeelectrode side of the battery cell BC1) via the input terminal V2 of IC1and the sensing line L2, while its input terminal 1 is connected betweenthe resistor R1 and the resistor R2. On the other hand, the output sideof this multiplexer MUX2 is connected to an input terminal 01 of themultiplexer HVMUX1 and also to an input terminal 00 of the multiplexerHVMUX2. In other words, when the multiplexer MUX2 selects its inputterminal 0, the potential at the input terminal 01 of the multiplexerHVMUX1 and the potential at the input terminal 00 of the multiplexerHVMUX2 become the same potential as that of the positive electrode sideof the battery cell BC2 (i.e. the potential at the negative electrodeside of the battery cell BC1); and, conversely, when the multiplexerMUX1 selects its input terminal 1, the potential at the input terminal00 of the multiplexer HVMUX1 and the potential at the input terminal 00of the multiplexer HVMUX2 become the potential between the resistor R1and the resistor R2.

Moreover, the input terminal 0 of the multiplexer MUX3 is connected tothe positive electrode side of the battery cell BC3 (and to the negativeelectrode side of the battery cell BC2) via the input terminal V3 of IC1and the sensing line L3, while its input terminal 1 is connected betweenthe resistor R2 and the resistor R3. On the other hand, the output sideof this multiplexer MUX3 is connected to an input terminal 10 of themultiplexer HVMUX1 and also to an input terminal 01 of the multiplexerHVMUX2. In other words, when the multiplexer MUX3 selects its inputterminal 0, the potential at the input terminal 10 of the multiplexerHVMUX1 and the potential at the input terminal 01 of the multiplexerHVMUX2 become the same potential as that of the positive electrode sideof the battery cell BC3 (i.e. the potential at the negative electrodeside of the battery cell BC2). And, conversely, when the multiplexerMUX3 selects its input terminal 1, the potential at the input terminal10 of the multiplexer HVMUX1 and the potential at the input terminal 01of the multiplexer HVMUX2 become the potential between the resistor R2and the resistor R3.

Furthermore, the input terminal 0 of the multiplexer MUX4 is connectedto the positive electrode side of the battery cell BC4 (and to thenegative electrode side of the battery cell BC3) via the input terminalV4 of IC1 and the sensing line L4, while its input terminal 1 isconnected between the resistor R3 and the resistor R4. On the otherhand, the output side of this multiplexer MUX4 is connected to an inputterminal 11 of the multiplexer HVMUX1 and also to an input terminal 10of the multiplexer HVMUX2. In other words, when the multiplexer MUX4selects its input terminal 0, the potential at the input terminal 10 ofthe multiplexer HVMUX1 and the potential at the input terminal 01 of themultiplexer HVMUX2 become the same potential as that of the positiveelectrode side of the battery cell BC4 (i.e. the potential at thenegative electrode side of the battery cell BC3). And, conversely, whenthe multiplexer MUX4 selects its input terminal 1, the potential at theinput terminal 11 of the multiplexer HVMUX1 and the potential at theinput terminal 10 of the multiplexer HVMUX2 become the potential betweenthe resistor R3 and the resistor R4.

Yet further, the input terminal 0 of the multiplexer MUX5 is connectedto the negative electrode side of the battery cell BC4 via the terminalGND of IC1 and the sensing line L4, while its input terminal 1 isconnected between the resistor R4 and the resistor RPD. On the otherhand, the output side of this multiplexer MUX5 is connected to an inputterminal 11 of the multiplexer HVMUX2. In other words, when themultiplexer MUX5 selects its input terminal 0, the potential at theinput terminal 10 of the multiplexer HVMUX1 and the potential at theinput terminal 01 of the multiplexer HVMUX2 become the same potential asthat of the negative electrode side of the battery cell BC4. And,conversely, when the multiplexer MUX5 selects its input terminal 1, thepotential at the input terminal 11 of the multiplexer HVMUX2 become thepotential between the resistor R4 and the resistor RPD.

With this second embodiment having the structure described above, it isarranged for it to be possible to diagnose whether or not themultiplexers HVMUX1 and HVMUX2 are operating normally by inputting thealready known voltages Vr1, Vr2, Vr3, and Vr4 that are generated by theresistors R1 through R4 to the multiplexers HVMUX1 and HVMUX2, insteadof the cell voltages.

The Cell Voltage Measurement Mode

In the normal mode for cell voltage measurement, the switch SW is in theOFF (opened) state, and each of the multiplexers MUX1 through MUX5 is inits state of selecting its input terminal 0. During the interval inwhich the cell voltage of the battery cell BC1 is to be measured, theinput terminals 00 of the multiplexer HVMUX1 and of the multiplexerHVMUX2 are selected, as shown in FIG. 14A. Due to this, the potential atthe positive electrode side of the battery cell BC1 is outputted fromthe multiplexer HVMUX1, while the potential at the negative electrodeside of the battery cell BC1 is outputted from the multiplexer HVMUX2.As a result, the voltage Vc1 of the battery cell BC1 that is thedifference between these potentials comes to be inputted to thedifferential amplifier 262. This cell voltage Vc1 is converted to adigital value by the analog to digital converter 122A, and is stored inthe register CELL1 of the current value storage circuit 274.

In a similar manner, during the interval in which the cell voltage ofthe battery cell BC2 is to be measured, the input terminals 01 of themultiplexer HVMUX1 and of the multiplexer HVMUX2 are selected; duringthe interval in which the cell voltage of the battery cell BC3 is to bemeasured, the input terminals 10 of the multiplexer HVMUX1 and of themultiplexer HVMUX2 are selected; and, during the interval in which thecell voltage of the battery cell BC4 is to be measured, the inputterminals 11 of the multiplexer HVMUX1 and of the multiplexer HVMUX2 areselected.

FIG. 15A is a figure showing the states of the multiplexers MUX1 throughMUX5 and HVMUX1 and HVMUX2 and so on during cell voltage measurement andduring diagnosis. During cell voltage measurement, the diagnosis mode isOFF (i.e. diag: 0), and all of the multiplexers MUX1 through MUX5 areselecting their input terminals 0. In this state, the cell voltages Vc2through Vc4 of the battery cells BC2 through BC4 may be measured inorder by changing over the selection state of both of the multiplexersHVMUX1 and HVMUX2 to 00, 01, 10, and 11 respectively. The results ofthese measurements are stored in the registers CELL1 through CELL4 ofthe current value storage circuit 274.

This type of cell voltage measurement is repeatedly performed at apredetermined cycle, so that the data in the registers CELL1 throughCELL4 is updated at that predetermined cycle. When a cell voltagerequest command is issued from the microcomputer 30, the newest voltagedata stored in the registers CELL1, through CELL4 is outputted via theserial communication circuit 602 at the timing that this command isreceived.

The Diagnosis Mode

When performing diagnosis of the multiplexers HVMUX1 and HVMUX2, adiagnosis command is transmitted to IC1 from the microcomputer 30 viathe serial communication circuit 602. This diagnosis command that hasbeen received by IC1 is transmitted in order to IC2 and IC3, and asimilar operation to the operation of IC1 described below is performedby IC2 and IC3. The same holds for IC4 through IC6.

Upon receipt of this diagnosis command, the logic/communication circuit401 of IC1 outputs a signal to turn the diagnosis mode to ON on thebasis of this diagnosis command, in other words a signal to turn theswitch SW to ON (closed), and also changeover signals to themultiplexers MUX1 through MUX5 to change over to their terminals 1. Asshown in FIG. 14B, the switch SW is turned ON by this changeover signal,and each of the multiplexers MUX1 through MUX5 selects its inputterminal 1. On the other hand, in a similar manner to the case ofperforming normal cell voltage measurement, the multiplexers HVMUX1 andHVMUX2 repeatedly perform changeover operation of their input terminalsin order to measure the cell voltages of the battery cells BC1 throughBC4 in order, on the basis of signals STG1 and STG2 that are outputtedfrom the decoders 257 and 259, and not in any relationship to thediagnosis command from the microcomputer 30.

As shown in FIG. 15A, during diagnosis, the diagnosis mode is turned ON(diag: 1), and all of the multiplexers MUX1 through MUX5 select theirinput terminals 1. In this state, the selection states of the twomultiplexers HVMUX1 and HVMUX2 change over through 00, 01, 10, and 11 inorder. For example, during the interval for measuring the cell voltageof the battery cell BC1, in other words during the interval formeasuring the voltage between the input terminals V1 and V2, as shown inFIG. 14B, the multiplexers HVMUX1 and HVMUX2 select their inputterminals 00. Due to this, the potential between the resistors RPU andR1 is outputted from the multiplexer HVMUX1, and the potential betweenthe resistors R1 and R2 is outputted from the multiplexer HVMUX2. As aresult the difference between these potentials, that is the voltage Vr1,is inputted to the differential amplifier 262. This voltage Vr1 isconverted to a digital value by the analog to digital converter 122A,and is stored in the register CELL1 of the current value storage circuit274, in a similar manner to the case with the cell voltage Vc1.

In a similar manner, during the interval for measuring the cell voltageof the battery cell BC2, the multiplexers HVMUX1 and HVMUX2 select theirinput terminals 01; during the interval for measuring the cell voltageof the battery cell BC3, the multiplexers HVMUX1 and HVMUX2 select theirinput terminals 10; and, during the interval for measuring the cellvoltage of the battery cell BC4, the multiplexers HVMUX1 and HVMUX2select their input terminals 11. As a result, the voltages Vr2 throughVr4 that are divided by the resistors R2 through R4 are measured, andare stored in the registers CELL2 through CELL4 of the current valuestorage circuit 274.

As described above, since the measurement of the voltages Vc1 throughVc4 according to the signals STG1 and STG2 is repeated at apredetermined cycle, accordingly, in the diagnosis mode, the voltagesVr1 through Vr4 come to be measured at that predetermined cycle. Afterthe microcomputer 30 has waited for a time period that is longer thanthe above described predetermined time period elapsed from thetransmission of the diagnosis command by the time period required tostore the voltages Vr1 through Vr4 in the registers CELL1 through CELL4,then it transmits to IC1 a command that request return of the diagnosisdata stored in these registers CELL1 through CELL4.

On the side of the microcomputer 30, Vr1 through Vr4 are stored inadvance as anticipated values for the diagnosis, and, if the measuredvalues of Vr1 through Vr4 that are returned from IC1 agree with theseanticipated values, then it is diagnosed that the multiplexer HVMUX1 andthe multiplexer HVMUX2 are operating normally. On the other hand, if themeasured values that are returned are different from the anticipatedvalues, then it may be diagnosed that there is an anomaly with at leastone of the multiplexer HVMUX1 and the multiplexer HVMUX2.

It should be understood that while, in the example described above, asshown in FIG. 15A, all of the input terminals 1 of the multiplexers MUX1through MUX5 were changed over during the diagnosis, it is not necessaryto adopt this method. For example it would also be acceptable, in orderto diagnose whether or not during measurement of the cell voltage Vc1the multiplexers HVMUX1 and HVMUX2 were correctly selecting their inputterminals 00, to arrange for a command to be transmitted from themicrocomputer 30 for only the multiplexers MUX1 and MUX2 to change overto their input terminals 1. In a similar manner, when diagnosing theselection state of the input terminals 01, a command may be transmittedfor only the multiplexers MUX2 and MUX3 to change over to their inputterminals 1; when diagnosing the selection state of the input terminals10, a command may be transmitted for only the multiplexers MUX3 and MUX4to change over to their input terminals 1; and, when diagnosing theselection state of the input terminals 11, a command may be transmittedfor only the multiplexers MUX4 and MUX5 to change over to their inputterminals 1. In this case, a command that requests return of the voltagedata also comes to be transmitted each time.

Furthermore, instead of performing changing over of the multiplexersHVMUX1 and HVMUX2 with the signals STG1 and STG2, it would also beacceptable to change them over by a command from the microcomputer 30.FIG. 15B is a figure showing, in this type of case, the state of themultiplexers MUX1 through MUX5 and HVMUX1 and HVMUX2 and so on duringcell voltage measurement and during diagnosis. In this case, since theselection states of the multiplexers HVMUX1 and HVMUX2 are set accordingto commands from the microcomputer 30, accordingly when, for example,diagnosing the selection state of the input terminals 00, provided thatthe selection states of the multiplexers MUX1 and MUX2 is 1, theselection states of the other multiplexers MUX3 through MUX5 may beeither 1 or 0.

Now, since the voltages Vr1 through Vr4 that have been voltage dividedby the resistors R1 through R4 are set so as to have values outside thenormal range of the cell voltages, accordingly it is also possible todecide from the voltage values that are returned whether or not themultiplexers MUX1 through MUX5 are operating normally. For example, ifin FIG. 14B the multiplexers MUX1 and MUX2 do not change over, then notthe voltage Vr1 but rather the cell voltage Vc1 comes to be returned,and accordingly it is possible to diagnose from this voltage value thatthe selection state of the multiplexer MUX1 or the selection state ofthe multiplexer MUX2 is not correct.

Diagnosis of the Excessive Charge Detection Circuit

Furthermore, if at least one of the voltages Vr1 through Vr4 is set to avoltage value that is larger than the normal range of cell voltage, andthat moreover corresponds to excessive charge, then it also becomespossible to diagnose whether or not the excessive charge detectioncircuit is operating normally. For example, the resistor R1 may be setso that the voltage Vr1 becomes a value that is a little larger than theabove described excessive charge threshold value OC. The voltage Vr1that has been A/D converted is stored in the register CELL1 of thecurrent value storage circuit 274. This stored voltage Vr1 is read outby the digital multiplexer 272 and is sent to the digital comparator270, that compares it with the excessive charge threshold value OC thathas been read out from the reference value storage circuit 278. And,since the voltage Vr1 is set to a value that is larger than theexcessive charge threshold value OC, accordingly, as explained withreference to FIG. 5, the flag [MFflag] that denotes an anomaly and theflag [OCflag] that denotes excessive charge are set in the flag storagecircuit 284, and an anomaly signal is transmitted via the one-bitcommunication circuit 604.

Now a case will be considered in which the registered value of theexcessive charge threshold value OC in the reference value storagecircuit 278 has changed undesirably due to an abnormality in the IC; forexample, suppose that the proper excessive charge threshold value OC is4 V, and that this has undesirably changed to 5 V. If the excessivecharge threshold value OC is at its proper value of 4 V, then themeasured voltage Vr1 is detected as excessive charge, and, along withthe above described flags being set, an anomaly signal is transmitted.However, if the excessive charge threshold value OC has undesirablychanged to 5 V, then, even if a voltage Vr1 that is slightly larger than4 V is measured as the cell voltage, it will be decided that this Vr1 isless than 5 V, and excessive charge will not be detected and the flagsdescribed above will not be set. In other words, no anomaly signal willbe transmitted.

However, since the microcomputer 30 sends to the multiplexer HVMUX1 acommand for input of the voltage Vr1 instead of the cell voltage Vc1,accordingly, along with the voltage Vr1 being returned as the cellvoltage of the battery cell BC1 of IC1 via the communication circuit602, also it may be anticipated that an anomaly signal will be returnedvia the one-bit communication circuit 604. Accordingly, if themicrocomputer 30 receives both the voltage Vr1 and also an anomalysignal, then it may be diagnosed that the excessive charge detectioncircuit of IC1 is operating normally. On the other hand if, as describedabove, due to an abnormality of the excessive charge threshold value OCregister, an anomaly signal is not received although the voltage Vr1 isreceived, then it may be diagnosed that an anomaly has occurred in theexcessive charge detection circuit, since the values anticipated by themicrocomputer do not agree. Here, normal operation of the excessivecharge detection circuit means that, with the excessive charge thresholdvalue OC being normal, and moreover with the digital comparator 270making its decision correctly, the one-bit register in which the flag[OCflag] is set has also not failed.

A Variant Embodiment

In the second embodiment described above, it was supposed that themultiplexer HVMUX1 and the multiplexer HVMUX2 always changed over in asynchronized manner, and that their selection states were changed overso as always to be the same. However, in a variant embodiment, it isarranged to be able to perform diagnosis as to whether or not theselections are carried out correctly, even though the multiplexer HVMUX1and the multiplexer HVMUX2 are used in such a manner that the differentinput terminals are selected in these multiplexers.

FIG. 16 is a figure for explanation of this variant embodiment, and is afigure showing blocks internal to IC1, in a similar manner to FIG. 13.In the second embodiment described above, if it is supposed that themultiplexer HVMUX1 selects its input terminal 00 while the multiplexerHVMUX2 selects its input terminal 01, then the voltage that is measuredis the voltage divided by the resistors R1+R2. However, if theresistance value setting has been performed so that R1+R2=R3, then, ifthe multiplexer HVMUX1 selects its input terminal 01 while themultiplexer HVMUX2 selects its input terminal 10, the voltage that ismeasured becomes the same, so that it is not possible to distinguishthese selection states.

Thus in this variant embodiment, by setting the resistance values of theresistors R1 through R4 so that R1=R, R2=2R, R3=4R, and R4=8R, it isarranged that, even if the selection states by the multiplexer HVMUX1and the multiplexer HVMUX2 of their input terminals are different, stillit is possible to perform diagnosis of the selection states. Thiscombination of resistance values is only one example; any combination ofresistance values will be acceptable, provided that the measured voltageis different for each combination of input terminals. The changing overof the multiplexers HVMUX1 and HVMUX2 is not performed according to thesignals STG1 and STG2 of the decoders 257 and 259, but rather bydiagnosis commands on the basis of a command from the microcomputer 30.It should be understood that, in the example shown in FIG. 16, theresistor RPD and the multiplexer MUX5 of FIG. 13 are omitted.

FIG. 17 is a figure showing a relationship between the combinations ofinput terminals of the multiplexers HVMUX1 and HVMUX2 that are selected,and the voltage values that are measured at that time. From FIG. 17, itwill be understood that, except for combinations in which the voltagevalue=0, whichever combination is selected, the voltage values are alldifferent from one another. In other words, when the microcomputer 30selects two of the input terminals of the multiplexers HVMUX1 and HVMUX2by transmitting, as a diagnosis command related to selection by themultiplexers HVMUX1 and HVMUX2, a selection command for a combinationfor which the voltage value is not equal to 0, then it is possible todiagnose from the voltage value that is measured whether or not thatcombination has been correctly selected, for any combination that mayhave been selected.

Diagnosis of the Excessive Charge Detection Circuit

If this type of diagnosis is possible, then, in addition to diagnosingfrom the measurements of cell voltage whether or not the multiplexersHVMUX1 and HVMUX2 are operating normally, it is also possible todiagnose whether or not the excessive charge detection circuit isoperating normally. For example if, while the field (00,11) of FIG. 17is 15RI, the resistance value R is set so that a voltage value of 15RIcorresponds to excessive charge, then it is possible to diagnose whetheror not the excessive charge detection circuit is operating normally bytransmitting from the microcomputer 30 commands for the multiplexerHVMUX1 to select its input terminal 00 and for the multiplexer HVMUX2 toselect its input terminal 11

If the excessive charge detection circuit is operating normally, thenthe flags [MFflag] and [OCflag] are set in the flag storage circuit 284,and an anomaly signal is transmitted to the microcomputer 30 via theone-bit communication circuit 604. If the microcomputer 30 has receivedan anomaly signal while the voltage value returned from IC1 is 15RI, inother words if it agrees with the anticipated value, then it is possibleto diagnose that the excessive charge detection circuit is operatingnormally. On the other hand, if no anomaly signal has been received eventhough a voltage value of 15RI has been received, then it is possible todiagnose that the excessive charge detection function is not operatingnormally.

The Third Embodiment

FIG. 18 is a figure for explanation of a third embodiment, and is ablock diagram similar to FIG. 13. In the structure shown in FIG. 18,bypass switches SW0 through SW4 are added to the structure of the secondembodiment shown in FIG. 13. By doing this, along with performingdiagnosis of the multiplexers HVMUX1 and HVMUX2 in a similar manner tothe second embodiment, it is also possible to perform separate diagnosisof the excessive charge detection circuit. Moreover, in this embodiment,it is possible for the multiplexers HVMUX1 and HVMUX2 to be changed overso as to select the same input terminals. In this case, they could bechanged over with the signals STG1 and STG2, or it would also beacceptable for them to be changed over by command from the microcomputer30. In the example shown in FIG. 18, the resistor RPD and themultiplexer MUX5 of FIG. 13 are omitted.

When performing diagnosis of the multiplexers HVMUX1 and HVMUX2, all ofthe bypass switches SW0 through SW4 are turned to OFF (open). Since whenthis is done the structure is similar to that of the second embodiment,accordingly it is possible to perform diagnosis of the multiplexersHVMUX1 and HVMUX2 by executing similar diagnosis operation to thatexplained above.

On the other hand, it is possible to generate voltages of various typesby controlling the bypass switches SW0 through SW4 to ON and OFF. Forexample when, as shown in FIG. 18, the bypass switch SW1 is turned OFFwhile the other bypass switches SW0 and SW2 through SW4 are turned ON,then the voltage due to the resistor R1 becomes greater, and it ispossible to generate an excessive voltage that corresponds to excessivecharge. And, when the input terminals of the multiplexers MUX1 and MUX2are set to 1, and the multiplexers HVMUX1 and HVMUX2 are set to theirstates for performing measurement of the cell voltage of the batterycell BC1, then it is possible to perform diagnosis of the excessivecharge detection circuit.

FIG. 26 is a flow chart showing diagnosis processing steps that areexecuted by the microcomputer 30. This diagnosis processing is executedat the timing that the vehicle key switch is turned ON or OFF. When thisprocessing starts upon the vehicle key switch being turned ON or OFF, ina first step S100 a command is transmitted to the IC to turn the switchSW to ON (closed). With regard to the switches SW0 through SW4, they areall left at OFF, in a similar manner to the case in the cell voltagemeasurement mode. And in a step S110 the microcomputer 30 transmits acommand to the IC to change over the selection states of themultiplexers MUX1 through MUX4 from their input terminals 0 to theirinput terminals 1.

The operation of measuring the cell voltages of the battery cells BC1through BC4 is performed repeatedly by the IC at a predetermined cycleby changing over the input terminals of the multiplexers HVMUX1 andHVMUX2 in order from 00. When, due to this, a longer time period thanthe predetermined cycle period has elapsed from changing over of themultiplexers MUX1 through MUX4 to their input terminals 1, then thevoltage values Vr1 through Vr4 that have been acquired by the cellvoltage measurement operation are stored in the registers CELL1 throughCELL4 as cell voltage data.

In the next step S120, the microcomputer 30 transmits to the IC acommand that requests transmission of the cell voltage data stored inthe registers CELL1 through CELL4. Upon receipt of this command, the ICreturns the cell voltage data stored in the registers CELL1 throughCELL4 at the time point of reception to the microcomputer 30 via theserial communication circuit 602.

And, in the next step S130, the microcomputer 30 makes a decision as towhether or not the multiplexers HVMUX1 and HVMUX2 are operatingnormally. In other words, it makes a decision as to whether or not thecell voltage data that has been received and the values that areanticipated on the side of the microcomputer 30 agree with one another.In the microcomputer 30, the voltage values Vr1, Vr2, Vr3, and Vr4 thatare divided voltages on the resistors R1 through R4 respectively arestored as anticipated values, and these anticipated values Vr1, Vr2,Vr3, and Vr4 and the cell voltage data in the registers CELL1 throughCELL4 that were received are compared together, and, if they all agreewith one another, then it is diagnosed that the multiplexers HVMUX1 andHVMUX2 are operating normally. But if there is even one pair of cellvoltage data that do not agree with one another, then an anomaly isdiagnosed.

If in the step S130 normal operation has been diagnosed, then the flowof control proceeds to a step S140, while if an anomaly has beendiagnosed then the flow of control is transferred to a step S200. If theflow of control has reached the step S200, then, along with turning theswitch SW to OFF, a command is transmitted to the IC to change over themultiplexers MUX1 through MUX4 to their input terminals 0. According tothis command, the IC performs the operation of turning the switch SW toOFF and the operation of changing over the multiplexers, and therebyreturns the IC to the cell voltage measurement state. Then in a stepS210 the microcomputer 30 transmits an anomaly report to a higher levelcontroller that notifies it of the fact that an anomaly has occurred inthe IC, and then this series of diagnosis processing steps terminates.It should be understood that, even if an anomaly with the multiplexerdiagnosis has been diagnosed, the diagnosis processing does notterminate there; rather, next, it may be arranged to perform thediagnosis of the excessive charge detection circuit.

On the other hand, if the flow of control has proceeded from the stepS130 to the step S140, next, in order to perform diagnosis of theexcessive charge detection circuit, only the switch SW1 is left in theOFF state, but the other switches SW0 and SW2 through SW4 are changedover to their ON states. It should be understood that the states of theswitch SW and of the multiplexers MUX1 through MUX4 are kept just asthey were for the state of multiplexer diagnosis. In other words, theswitch SW is kept at ON, and the selection states of the multiplexersMUX1 through MUX4 are kept at their input terminals 1.

Since the ICs perform the cell voltage measurement operationperiodically as described above, accordingly when, after having executedthe processing of the step S140, as shown in FIG. 18 the multiplexersHVMUX1 and HVMUX2 perform voltage measurement of the battery cell BC1 attheir input terminals 00, the voltage of the resistor R1 (an excessivevoltage that corresponds to excessive charge) comes to be inputted tothe multiplexers HVMUX1 and HVMUX2. This voltage is converted to adigital value by the analog to digital converter 122A, and is stored inthe register CELL1. And, when it is compared with the excessive chargethreshold value OC by the digital comparator 270, the fact thatexcessive charge has been detected is set in the flag [OCflag] in theflag storage circuit 284. As a result, an anomaly signal is sent fromthe IC to the one-bit communication circuit 604, and this anomaly signalis received by the microcomputer 30.

And in a step S150 the microcomputer 30 transmits a command to the ICthat requests the transmission of the cell voltage data stored in theregisters CELL1 through CELL4. Upon receipt of this command, the ICreturns the cell voltage data stored in the registers CELL1 throughCELL4 at the time point of receipt to the microcomputer 30 via theserial communication circuit 602. It should be understood that it wouldalso be acceptable, in the step S150, for only the cell voltage data ofthe register CELL1 to be requested.

Then in a step S160, along with turning the switches SW, SW0, and SW2through SW4 to OFF, a command for changeover of the multiplexers MUX1through MUX4 from their input terminals 1 to their input terminals 0 istransmitted to the IC. And the IC returns to the cell voltagemeasurement state by performing the operation of turning off theswitches and the changeover operation of the multiplexers according tothis command.

In the next step S170, the microcomputer 30 diagnoses whether or not theexcessive charge detection circuit is operating normally. In otherwords, normal operation or an anomaly of the excessive charge detectioncircuit is determined on the basis of whether or not the received cellvoltage data and an anomaly signal have been received. Although it hasalready been diagnosed in the step S130 that the multiplexers HVMUX1 andHVMUX2 are operating normally, the fact that excessive voltage is, asexpected, being inputted is confirmed from the cell voltage data. Andwhether or not excessive charge detection is being performed as expecteddue to the input of this excessive voltage is diagnosed according as towhether or not an anomaly signal is received.

If an anomaly signal has been received, it is diagnosed that theexcessive charge detection circuit is operating normally. The flow ofcontrol is transferred from this step S170 to the step S210. In thisstep S210, an anomaly report to the effect that an anomaly has occurredin the functioning of the IC is transmitted from the microcomputer 30 tothe higher level controller, and then this series of diagnosticprocessing steps terminates.

The Fourth Embodiment

FIG. 19 is a figure for explanation of a fourth embodiment. In thesecond embodiment, the resistors R1 through R4 were connected in seriesto the voltage source 400 that was provided to the IC, the already knownvoltages that were voltage divided by these resistors R1 through R4 wereinputted instead of the cell voltages, and thereby diagnosis of themultiplexers HVMUX1 and HVMUX2 was performed. However, in this fourthembodiment, it is arranged to perform diagnosis of the multiplexersHVMUX1 and HVMUX2 by providing voltage sources 402 through 405 insteadof the resistors R1 through R4, and by inputting the already knownvoltages from these voltage sources 402 through 405.

The magnitudes of the values of the voltages outputted by the voltagesources 402 through 405 when performing diagnosis of the multiplexersHVMUX1 and HVMUX2 are set in a similar manner to the case of setting thevoltage values generated by the resistors R1 through R4. It is alsosimilarly possible to diagnose whether or not the multiplexers MUX1 andMUX2 are operating correctly. Since the operation of the multiplexersMUX1, MUX2, HVMUX1, and HVMUX2 during diagnosis is the same as that inthe second embodiment, it will herein be omitted. The voltage sources402 through 405 are turned ON when the diagnosis mode is ON, and areturned OFF when the diagnosis mode is OFF. For these voltage sources 402through 405, there may be used voltage dividers that divide by avariable resistance value, DACs, charge pumps, DC-DC converters, orelements that can generate voltage such as band gap references or thelike.

Furthermore, it is also possible to use the voltage sources 402 through405 as variable voltage sources, and to perform diagnosis of theexcessive charge detection circuit by changing the output voltage of oneof them to a voltage value that corresponds to excessive charge. Itshould be understood that while, in FIG. 19, the voltage sources 402through 405 are provided internally to IC1, it would also be acceptableto provide them externally to IC1, and to build the structure so thatthey input already known voltage values to the terminals V1 through V4.

FIG. 27 is a figure showing an example when the voltage sources areprovided externally to the IC. In the case of the IC shown in FIG. 27, astructure is provided in which it is possible to connect six batterycells to the terminals VCC, CV1 through CV6, and GND S; and, in theexample shown in FIG. 27, four battery cells are connected to theterminals CV3 through CV6 and GND S. Here, the external voltage source440 is provided to the terminal CV6 for diagnosis of the excessivecharge detection circuit, and corresponds to the voltage source 405 ofFIG. 19. And also, when performing multiplexer diagnosis, it is providedto each of the terminals CV3, CV4, CV5, and CV6 that correspond to therespective battery cells. An insulation switch 430 is actuated by asignal from the microcomputer 30, so that a photo-coupler 431 is turnedON. As a result, a voltage that is generated from the voltage Vref ofthe external voltage source 440 is applied to the terminal V6 of the IC.

The Fifth Embodiment

FIG. 20 is a figure for explanation of a fifth embodiment. While, in thefourth embodiment described above, the voltage sources 402 through 405were provided at a stage before the multiplexers HVMUX1 and HVMUX2, inthis fifth embodiment voltage sources 410 and 411 are provided at astage after the multiplexers HVMUX1 and HVMUX2. The multiplexers MUX1and MUX2 are provided upon the lines between the multiplexers HVMUX1 andHVMUX2 and the differential amplifier 262. The output of the multiplexerHVMUX1 is inputted to the input terminal 0 of the multiplexer MUX1, andan already known voltage from the voltage source 410 is inputted to itsother input terminal 1. Similarly, the output of the multiplexer HVMUX2is inputted to the input terminal 0 of the multiplexer MUX2, and analready known voltage from the voltage source 412 is inputted to itsother input terminal 1.

In this embodiment, by providing a structure like that shown in FIG. 20,it becomes possible to perform diagnosis separately and individually asto whether or not any malfunction has occurred with the multiplexersHVMUX1 and HVMUX2. During normal measurement of cell voltages, themultiplexers MUX1 and MUX2 are put into their states in which theirinput terminals 0 are selected, and the voltage sources 410 and 411 arein their OFF states. On the other hand, in the diagnosis mode, theselection states of the multiplexers MUX1 and MUX2 and the ON/OFF statesof the voltage sources 410 and 411 are controlled according to commandsfrom the microcomputer 30.

First, when performing diagnosis of the multiplexer HVMUX1, themultiplexer MUX1 is set to its input terminal 0 and the multiplexer MUX2is set to its input terminal 1, and the voltage value of the voltagesource 411 is set to the ground level of IC1. The voltage source 410 isset to its OFF state. When in this state the input terminals of themultiplexers HVMUX1 and HVMUX2 are changed over to 00, 01, 10, and 11according to the cell voltage measurement operation of the IC, thevoltage of four cells, the voltage of three cells, the voltage of twocells, and the voltage of one cell come to be input in order into thedifferential amplifier 262. It should be understood that it would alsobe acceptable to arrange for the selection state of the multiplexerHVMUX1 to be changed over in order according to commands from themicrocomputer 30.

Since the voltage that is measured is different by one cell or more inthis manner when the input terminal of the multiplexer HVMUX1 that isselected is different, accordingly the microcomputer 30 is able todiagnose, from these voltage values that are measured, whether or notthe multiplexer HVMUX1 is correctly selecting its input terminal ascommanded.

On the other hand, when performing diagnosis of the multiplexer HVMUX2,the multiplexer MUX1 is set to its input terminal 1 and the multiplexerMUX2 is set to its input terminal 0, and the voltage value of thevoltage source 410 is set to the ground level of IC1. The voltage source411 is set to its OFF state. When in this state the input terminals ofthe multiplexers HVMUX1 and HVMUX2 are changed over to 00, 01, 10, and11 according to the cell voltage measurement operation of the IC in asimilar manner to the case of measurement of the cell voltages, theminus voltage of four cells, the minus voltage of three cells, the minusvoltage of two cells, and the minus voltage of one cell come to be inputin order into the differential amplifier 262. Due to this it is possibleto diagnose the selection state of the multiplexer HVMUX2, in a similarmanner to the case with the multiplexer HVMUX1.

While in the example described above the voltage value of the voltagesource was set to ground level, this is not to be considered as beinglimitative. For example if, when performing diagnosis of the multiplexerHVMUX1, the voltage value of the voltage source 411 is set to thevoltage level of two cells, then, when the input terminals of themultiplexers HVMUX1 and HVMUX2 are changed over to 00, 01, 10, and 11,then the voltage of two cells, the voltage of one cell, the voltage ofno cells, and the minus voltage of one cell are inputted in order to thedifferential amplifier 262. Since, with this type of setting as well,the voltages that are measured are different by one cell or more whenthe input terminals that are selected are different, accordingly it ispossible to perform diagnosis of the selection state of the multiplexerHVMUX1 from these voltage values.

It should be understood that, since sometimes the input voltage range ofthe differential amplifier 262 comes to be exceeded when the voltage offour cells is inputted, accordingly it is desirable to arrange toprovide an attenuator at a stage before the differential amplifier 262that is provided in circumstances of this type. While, in the exampledescribed above, the changing over of the multiplexers HVMUX1 and HVMUX2was performed according to the signals STG1 and STG2 from the decoders257 and 259, it would also be acceptable to perform this changing overaccording to commands from the microcomputer 30.

Diagnosis of the Excessive Charge Detection Function

Furthermore it is also possible to perform diagnosis of the excessivecharge detection circuit, since the voltages of two to four cells areinputted corresponding to excessive charge. Even further, it would alsobe acceptable to arrange to perform diagnosis of the excessive chargedetection circuit by changing over both of the multiplexers MUX1 andMUX2 to their input terminals 1, and by inputting to the differentialamplifier 262 excessive voltages that correspond to excessive charge byusing the voltage sources 410 and 411. For example, the voltage source411 may be set to ground potential, while the voltage source 410 is setto a value that corresponds to excessive charge. By inputting anexcessive voltage to the differential amplifier 262 in this manner, itis possible to diagnose that the differential amplifier 262, the analogto digital converter 122A, and the digital comparator 270 are operatingnormally, and it is also possible to diagnose that the registers inwhich the excessive charge threshold value flag OC and the flag [OCflag]are set are operating normally. It is also possible to decide whether ornot the voltage source 410 has correctly inputted an excessive voltage,from the voltage data of the registers CELL that is returned by serialcommunication.

As the structure for performing diagnosis of the excessive chargedetection circuit, instead of inputting an excessive voltage by usingthe voltage sources 410 and 411 such as shown in FIG. 20, it would alsobe acceptable to employ a structure like that shown in FIG. 28. FIG. 28is a figure showing the analog to digital converter 122A and blockssubsequent to it. A register is provided to the current value storagecircuit 274 in which a value VOC that corresponds to excessive charge isstored. This value VOC that corresponds to excessive charge is set so asto be slightly larger than the excessive charge threshold value OC thatis kept in the reference value storage circuit 278. One or the other ofthis value VOC that corresponds to excessive charge and the voltagevalue data stored in the register CELL3 is selected by a multiplexer 450and is inputted to a digital multiplexer 272. The changing over of theinput terminals 0 and 1 of the multiplexer 450 is performed according todiagnosis commands on the basis of commands from the microcomputer 30.

In the normal cell voltage measurement mode, the selection state of themultiplexer 450 is set to its input terminal 0. Due to this, the data inthe register CELL3 that is the cell voltage of the battery cell BC3comes to be read out by the digital multiplexer 272. On the other hand,when performing diagnosis of the excessive charge detection circuit, theselection state of the multiplexer 450 is changed over to its inputterminal 1. As a result, instead of the voltage data of the registerCELL3, the value VOC that corresponds to excessive charge is read out,and the excessive charge threshold value OC in the reference valuestorage circuit 278 and this value VOC that corresponds to excessivecharge are compared together by the digital comparator 270. Since thevalue VOC that corresponds to excessive charge is set to be greater thanthe excessive charge threshold value OC, accordingly the result of thiscomparison is that the flag [OCflag] that denotes excessive charge isset in the flag storage circuit 284. When this flag [OCflag] is set, ananomaly signal is sent to the one-bit transmission circuit 604, and isreceived by the microcomputer 30. Moreover, the value VOC thatcorresponds to excessive charge is returned to the microcomputer 30 asthe cell voltage of the battery cell BC3.

FIG. 29 is a flow chart showing the steps of excessive charge detectionfunction diagnosis. In a step S310, a flag for excessive chargedetection function diagnosis is set to “true” and diagnosis is started.Then in a step S320 a variable n is set to 1. Here, n is the number ofthe IC for which diagnosis is to be performed; n is set to 1 whenperforming diagnosis of IC1, n is set to 2 when performing diagnosis ofIC2, and n is set to 3 when performing diagnosis of IC3. Then in a stepS330 the value VOC that corresponds to excessive charge is set, insteadof the cell voltage Vc3 that has been measured (CV3 in FIG. 29). Next ina step S340 a check is made that the excessive charge signal has beenreceived. In the next step S350, the value of n is increased to n+1 inorder to perform diagnosis of the next IC, i.e. of IC2 (in this case Nis increased by 1 to 2). Then in a step S360 a decision is made as towhether or not the value of n is 3, in other words as to whether or notthe diagnosis of IC3 has been completed. If a negative decision isreached in this step S360, then, after having cleared the excessivecharge flag and sent a signal in a step S370, the flow of controlreturns to the step S330. On the other hand, if an affirmative decisionis reached in the step S360, in other words if the diagnosis has beencompleted up to and including IC3, then the flow of control proceeds toa step S380, in which the excessive charge flag is cleared and a signalis sent. Finally in a step S390 the flag for excessive charge detectionfunction diagnosis is set to “false”, and this diagnosis terminates.

When the cell voltage of the battery cell BC3 that is returned agreeswith the anticipated value VOC that corresponds to excessive charge,then the microcomputer 30 is able to recognize that the multiplexer 450is operating correctly according to the commands that it receives.Furthermore, when an anomaly signal has been received, it may bediagnosed that the excessive charge detection circuit is operatingnormally. On the other hand, if an anomaly signal is not received eventhough the value VOC that corresponds to excessive charge is beingreturned, then it is possible to diagnose an anomaly in the excessivecharge detection circuit. It should be understood that, if the value VOCthat corresponds to excessive charge is not returned, then it ispossible to determine that the multiplexer 450 is not operatingnormally.

In this manner, by providing a structure by which the value VOC thatcorresponds to excessive charge is inputted to the digital multiplexer272 instead of the voltage data of CELL3, and by which this value iscompared by the digital comparator 270 to the excessive charge thresholdvalue OC, it is possible, upon receipt of an anomaly signal, to confirmthat the excessive charge threshold value OC is correctly stored in thereference value storage circuit 278, that the digital comparator 270 isoperating correctly, and that the flag [OCflag] is being correctly set.Conversely, if an anomaly signal is not received, then it is possible todiagnose that an anomaly is occurring with at least one of thesefunctions.

The Sixth Embodiment

In the second through the fifth embodiments described above, it wasarranged for the difference between the outputs of the multiplexersHVMUX1 and HVMUX2 to be obtained by the differential amplifier 262, forthis difference to be converted into a digital value by the analog todigital converter 122A, and for diagnosis of the multiplexers to beperformed on the basis of this data. However, in a sixth embodimentshown in FIG. 21, it is arranged to perform diagnosis of themultiplexers HVMUX1 and HVMUX2 on the basis of the differences betweenthe inputs and the outputs of the multiplexers HVMUX1 and HVMUX2.

In FIG. 21, the portions denoted by the reference symbol 420 arecircuits that obtain the differences between the inputs and the outputsof the multiplexers HVMUX1 and HVMUX2. While in the following the caseof the multiplexer HVMUX2 will be explained, the same also goes for themultiplexer HVMUX1. Four comparators COMP1 through COMP4 are provided tothe differential circuit 420. The input terminal 1 of the comparatorCOMP1 is connected to the output line of the multiplexer HVMUX2, whileits input terminal 2 is connected to the line that connects the positiveelectrode of the battery cell BC2 and the input terminal 00 of themultiplexer HVMUX2. In the selection state of the multiplexers HVMUX1and HVMUX2 shown in FIG. 21, the same potential is inputted to the inputterminal of the comparator COMP1 as to the input terminal 00 of themultiplexer HVMUX2.

In a similar manner, for the comparator COMP2, the output of themultiplexer HVMUX2 is inputted to its input terminal 1, while the samepotential is inputted to its input terminal 2 as to the input terminal01 of the multiplexer HVMUX2. And, for the comparator COMP3, the outputof the multiplexer HVMUX2 is inputted to its input terminal 1, while thesame potential is inputted to its input terminal 2 as to the inputterminal 10 of the multiplexer HVMUX2. Moreover, for the comparatorCOMP4, the output of the multiplexer HVMUX2 is inputted to its inputterminal 1, while the same potential is inputted to its input terminal 2as to the input terminal 11 of the multiplexer HVMUX2. It should beunderstood that the output sides of the multiplexers HVMUX1 and HVMUX2are pulled up or pulled down in order to correspond to floating theoutputs of the multiplexers HVMUX1 and HVMUX2.

When measuring the cell voltage of the battery cell BC1, as shown inFIG. 21, the input terminals 00 of the multiplexers HVMUX1 and HVMUX2are selected. And the potential at the positive electrode side of thebattery cell BC2 is inputted to the input terminals 1 of the comparatorsCOMP1 through COMP4. As a result, the potential differences between theinput and the output terminals of the comparators COMP1 through COMP4become, from the comparator COMP1 through the comparator COMP4 in order,the voltage of no cells, the voltage of one cell, the voltage of twocells, and the voltage of three cells.

Each of the comparators COMP1 through COMP4 has a characteristic asshown in FIG. 22. In FIG. 22, the differential voltage between the inputin1 at the input terminal 1 and the input in2 at the input terminal 2(dV=in1−in2) is shown along the horizontal axis, while the outputs ofthe comparators COMP1 through COMP4 (digital values) are shown along thevertical axis. If the value of the differential voltage dV that isinputted is within a predetermined range H that is centered around 0,then a digital value of 1 is outputted from the comparators COMP1through COMP4, and conversely, if the value of the differential voltagedV is a value that is outside the predetermined range H, then a digitalvalue of 0 is outputted. The predetermined range H is set to a value ofsuch an order as that the errors of the comparators COMP1 through COMP4can be ignored.

In the state shown in FIG. 21, 1 is being outputted from the comparatorCOMP1 and 0 is being outputted from the comparators COMP2 through COMP4.These values are stored in the current value storage circuit 274 as theselection state data “0001”. On the other hand, the same is true in thecase of the multiplexer HVMUX1, so that the selection state data “0001”is outputted from the differential circuit 420 and is stored in thecurrent value storage circuit 274. In a similar manner: the selectionstate data “0010” is outputted from the differential circuit 420 whenthe input terminals 01 of the multiplexers HVMUX1 and HVMUX2 areselected; the selection state data “0100” is outputted when their inputterminals 10 are selected; and the selection state data “1000” isoutputted when their input terminals 11 are selected.

In this manner, the selection state data that is obtained during cellvoltage measurement is data that indicates which of the input terminalsof the multiplexers HVMUX1 and HVMUX2 are selected, and is stored in theregisters of the current value storage circuit 274 in correlation withthe cell voltages. Furthermore, this selection state data is acquiredduring each interval of the cell voltage measurement cycle. When each ofthe ICs receives a command to transmit the voltages of its cells, alongwith the cell voltages, it also sends the selection state data to themicrocomputer 30 together therewith. And the microcomputer 30 performsdiagnosis of the multiplexers HVMUX1 and HVMUX2 on the basis of thisselection state data that it receives. For example, if the selectionstate data that corresponds to the cell voltage of the battery cell BC1is “0001”, then a diagnosis of normal operation is reached, while if itis any other data, then an anomaly is diagnosed.

The Seventh Embodiment

FIG. 23 is a figure for explanation of a seventh embodiment. In thisseventh embodiment, if a cell voltage equal to 0 V is detected, then itis possible to make a diagnosis as to whether this originates due to abreakage of one of the sensing lines L1 through L5, or whether itoriginates due to the output voltage Vc1 becoming 0 V because of ananomaly in one of the battery cells BC1 through BC4 (such as an internalshort or the like). In the normal mode for measuring the cell voltages,the change over operation of the multiplexers HVMUX1 and HVMUX2 isperformed on the basis of the signals STG1 and STG2 from the decoders257 and 259 that are provided to IC1, but in the diagnosis mode priorityis given to commands from the microcomputer 30. And the selection statesof the multiplexers HVMUX1 and HVMUX2 and the ON/OFF states of thebalancing switches are controlled by these commands, and diagnosis isperformed on the basis of the voltage values that are measured at thistime.

It should be understood that in this explanation only the diagnosisdescribed above is described, while the resistors RPU, R1 through R4,and RPD that are needed for the diagnosis of the multiplexers HVMUX1 andHVMUX2, the multiplexers MUX1 through MUX5, the switch SW, and thevoltage source 400 are all omitted from FIG. 23, and explanation thereofis also omitted, because they are the same as in the case of FIG. 13.Furthermore, the balancing resistors R that adjust the balancingcurrents are not structures that are necessarily internal to IC1; theymay also be implemented externally to IC1.

As an example, the case when a cell voltage Vc2 equal to 0 V ismeasured, and it is to be diagnosed whether this should be ascribed to abreakage of the sensing line L2, or to a short circuit having occurredinternally to the battery cell BC2, will be explained with reference toFIG. 24. When performing this diagnosis, the selection states of themultiplexers HVMUX1 and HVMUX2 and the ON/OFF states of the balancingswitches 129A and 129B are controlled. FIG. 24 shows the relationshipbetween the selection states of the multiplexers HVMUX1 and HVMUX2 andthe ON/OFF states of the balancing switches 129A and 129B, and thevoltages that are measured. In the following, the selection states ofthe multiplexers HVMUX1 and HVMUX2 and the ON/OFF states of thebalancing switches 129A and 129B are shown as control states (HVMUX1,HVMUX2, 129A, and 129B). Moreover, the first row of FIG. 24 shows themeasured voltage values during normal conditions, the second row showsthe measured voltage values when the sensing line L2 has suffered a linebreakage, and the third row shows the measured voltage values when Vc2is equal to 0 V due to an abnormality in the battery cell BC2.

The first column from the left side of FIG. 24 shows the case when thecontrol state is (N1, N1, x, x). In other words, this is the case inwhich the input terminals N1 of both of the multiplexers HVMUX1 andHVMUX2 are selected. The reference symbol “x” being shown in relation tothe ON/OFF states of the balancing switches 129A and 129B means thatthese switches could be in either the ON or the OFF state, and it doesnot matter which. In the case of this control state of (N1, N1, x, x),the measured voltage value is 0 V in all three cases: during normalconditions, when the sensing line is broken, and when there is someabnormality of the battery cell. It should be understood that, if it isnot possible for the input terminals N1 of both of the multiplexersHVMUX1 and HVMUX2 to be selected, this control state is not essential,and it may also be omitted.

The second column shows the case in which the control state is (N1, N2,ON, x); in other words, this is the state shown in FIG. 23. In thiscase, during normal conditions, the cell voltage Vc1 of the battery cellBC1, in other words the voltage of one cell, comes to be measured. Onthe other hand, if there is a line breakage in the sensing line L2, thena measured voltage value equal to 0 V is measured. Furthermore since,even if the output voltage Vc2 of the battery cell BC2 is equal to 0 Vdue to an abnormality, this exerts no influence upon the voltagemeasurement between the terminals V1 and V2, accordingly a measuredvoltage value equal to Vc1 is measured in this case as well.

The third column shows the case in which the control state is (N1, N3,x, x). In this case, during normal conditions, the sum of the cellvoltage Vc1 of the battery cell BC1 and the cell voltage Vc2 of thebattery cell BC2, in other words the voltage of two cells Vc1+Vc2, comesto be measured. Moreover since, even if there is a line breakage in thesensing line L2, this exerts no influence upon the voltage measurementbetween the terminals V1 and V3, accordingly the voltage of two cellsVc1+Vc2 is measured in this case as well. On the other hand, if theoutput voltage Vc2 of the battery cell BC2 is equal to 0 V due to anabnormality, then only the voltage of one cell (Vc1+0) will come to bemeasured.

The fourth column shows the case in which the control state is (N2, N3,x, ON). In this case, during normal conditions, the cell voltage Vc2 ofthe battery cell BC2, in other words the voltage of one cell, comes tobe measured. On the other hand, if there is a line breakage in thesensing line L2, then 0 V will come to be measured. And, if due to anabnormality in the battery cell BC2 its output voltage Vc2 is equal to 0V, then 0 V will come to be measured.

In this manner, by comparing together the groups of measured voltagesthat relate to the four types of control state (N1, N1, x, x), (N1, N2,ON, x), (N1, N3, x, x), and (N2, N3, x, ON), it is possible to diagnosewhether there is a line breakage in the sensing line L2, or whether theoutput voltage of the battery cell BC2 itself is really 0 V. Anddiagnosis for other cases as well, for example for whether there is aline breakage in the sensing line L3 or whether the output voltage ofthe battery cell BC3 itself is really 0 V and so on, can also becontemplated in a similar manner.

The Eighth Embodiment

FIGS. 25A and 25B are figures for explanation of an eighth embodiment.While the structure shown in FIG. 25A is the same as the structure shownin FIG. 16, the structure of each of the multiplexers MUX1 through MUX4is as shown in FIG. 25B. In this embodiment, the multiplexers MUX1through MUX4 are made as transfer gates combining NMOS and PMOS, or thelike, and switches that are provided at each of their input terminals 0and 1 can be independently controlled to ON and OFF according tocommands from the microcomputer 30.

With this eighth embodiment as well, the operation in the normal modefor performing cell voltage measurement, and the operation whenperforming diagnosis of the connection states of the multiplexers HVMUX1and HVMUX2 in the diagnosis mode, are performed in a similar manner tothe case shown in FIG. 16. Furthermore, in this eighth embodiment, it ispossible to perform line breakage diagnosis of the sensing lines byturning the switch SW that is provided to the voltage source 400 to OFF,while simultaneously turning to ON both of the two switches in themultiplexers MUX1 through MUX4, shown in FIG. 25B. It should beunderstood that, in order to perform this line breakage diagnosis, it isnecessary to set the resistance values of the resistors RPU and R1through R4 to be sufficiently greater than the internal resistances ofthe battery cells.

In FIG. 25A, by putting both of the switches of the multiplexers MUX1and MUX2 to the ON state, it is possible to diagnose line breakage ofthe sensing line L1. While the cell voltage Vc1 is measured if there isno line breakage of the sensing line L1, 0 V comes to be detected as themeasured voltage value if there is such a line breakage. In the seventhembodiment described above, line breakage detection is performed byturning the balancing switch 129A to ON and causing a balancing current(a bypass current) to flow in the balancing resistor R. However, in thisembodiment, a bypass current is caused to flow in the resistor R1 bysetting both of the switches of the multiplexers MUX1 and MUX2 to the ONstate, and thereby line breakage detection is performed. In the case ofthis embodiment, there is the advantageous aspect that it is possible tomake the useless current (i.e. the leakage current) during line breakagediagnosis small, since the resistor R1 is set to be large, and theamount of current that flows in it is smaller than the balancingcurrent.

The embodiments described above may be employed either singly or in anyof various combinations. This is because the benefits of theseembodiments may be reaped either singly or synergistically. Furthermore,the present invention is not to be considered as being limited by any ofthe features of the embodiments described above, provided that itsessential characteristics are not lost.

1. A battery monitoring system, comprising: a battery state detectioncircuit that detects battery states of a plurality of battery cells thatare connected in series, based on respective cell voltages of theplurality of battery cells; and a control circuit that monitors state ofa battery cell, based on each cell voltage of the plurality of batterycells; and wherein the control circuit inputs pseudo voltage informationto the battery state detection circuit, and thereby diagnoses whether ornot the battery state detection circuit is operating normally.
 2. Abattery monitoring system according to claim 1, further comprising: anintegrated circuit that comprises, as the battery state detectioncircuit, an excessive charge detection circuit that detects excessivecharge of a battery cell by comparing together its cell voltage that hasbeen measured and an excessive charge threshold value, and outputs thisdetection information to the control circuit, and that also measures therespective cell voltages of the plurality of battery cells; and an inputcircuit that is provided internally or externally to the integratedcircuit, and that, upon a command from the control circuit, inputs tothe excessive charge detection circuit, as the pseudo voltageinformation, a voltage corresponding to excessive charge, instead of thecell voltage that has been measured; and wherein the control circuitcauses input of a voltage corresponding to the excessive charge to beperformed by the input circuit, and diagnoses whether or not theexcessive charge detection circuit is operating normally based onpresence or absence of output of the detection information.
 3. A batterymonitoring system according to claim 2, wherein: the input circuitcomprises: a first storage circuit that stores measured cell voltages; asecond storage circuit that stores a voltage that corresponds toexcessive charge; and a changeover unit that selects either one of thevoltages stored in the first storage circuit and the second storagecircuit, and inputs it to the excessive charge detection circuit; andthe control circuit controls the changeover unit so that a voltagecorresponding to excessive charge stored in the second storage circuitis inputted to the excessive charge detection circuit, and diagnoseswhether or not the excessive charge detection circuit is operatingnormally, based on presence or absence of output of the detectioninformation.
 4. A battery monitoring system according to claim 2,wherein: the integrated circuit comprises a selection circuit to whichrespective cell voltages of the plurality of battery cells are inputtedand that selects and outputs any one of the plurality of cell voltagesthat have been inputted, and a voltage measurement circuit that measuresa cell voltage outputted from the selection circuit and inputs it to theexcessive charge detection circuit; and the input circuit is a voltagecircuit that generates a voltage corresponding to excessive chargewithin the integrated circuit, and, upon command from the controlcircuit, inputs the voltage corresponding to excessive charge to theselection circuit, instead of the cell voltage that has been measured.5. A battery monitoring system according to claim 4, wherein the voltagecircuit generates a voltage that corresponds to the excessive charge bydividing a voltage of a voltage source by certain resistance values. 6.A battery monitoring system according to claim 4 wherein the inputcircuit comprises a plurality of voltage sources each of which generatesa voltage corresponding to the excessive charge upon command from thecontrol circuit.
 7. A battery monitoring system according to claim 2,wherein: the integrated circuit comprises a selection circuit to whichrespective cell voltages of the plurality of battery cells are inputtedand that selects and outputs any one of the plurality of cell voltagesthat are inputted, and a voltage measurement circuit that measures acell voltage outputted from the selection circuit and inputs it to theexcessive charge detection circuit; the input circuit comprises avoltage source that generates a voltage corresponding to excessivecharge, and a changeover unit that selects the voltage corresponding tothe excessive charge and any one of the cell voltages outputted from theselection circuit, and inputs it to the voltage measurement circuit; andthe control circuit controls the changeover unit so that a voltagecorresponding to the excessive charge is inputted to the voltagemeasurement circuit, and diagnoses whether or not the excessive chargedetection circuit is operating normally, based on presence or absence ofoutput of the detection information.
 8. A battery monitoring systemaccording to claim 1, further comprising: integrated circuits, which areprovided to respective cell groups in which a plurality of battery cellsare grouped, and which cell groups are electrically connected in seriesforming a battery unit, and which integrated circuit measures respectivevoltages of battery cells making up cell groups and outputs voltageinformation; and a plurality of voltage measurement lines that connectpositive and negative electrodes of the battery cells and the integratedcircuits via resistors; and wherein: the integrated circuitsrespectively are including a selection circuit that selects a voltagemeasurement line of a battery cell that is to be a subject ofmeasurement and that is provided as a battery state selection circuit, adetection circuit that detects a voltage from a voltage measurement lineselected by the selection circuit, and a discharge circuit thatdischarges a battery cell so that a discharge current flows in theresistors; and the control circuit diagnoses state of selection by theselection circuit, based on a first voltage that is detected by thedetection circuit when discharge by the discharge circuit is stopped,and a second voltage that is detected by the detection circuit duringdischarge by the discharge circuit, as the pseudo voltage informationthat receives influence of voltage drop in the resistor.
 9. A batterymonitoring system according to claim 8, wherein values of the resistorsare set so that voltage drops due to the resistors are greater than thevoltage variations of the plurality of battery cells.
 10. A batterymonitoring system according to claim 9, wherein: the discharge circuitperforms discharge when voltage of each battery cell exceeds an upperlimit; and values of the resistors are set so that voltage drop due tothe resistors are greater than a variation of the plurality of batterycells.
 11. A battery monitoring system according to claim 8, wherein thecontrol circuit compares a difference between the first voltage and thesecond voltage with a predetermined threshold value, and diagnoses thata selection state by the selection circuit is normal if difference isgreater than or equal to a predetermined threshold value.
 12. A batterymonitoring system according to claim 11, wherein the predeterminedthreshold value is set so as to be greater than a variation of voltagesof the plurality of battery cells.
 13. A battery monitoring systemaccording to claim 8, wherein detection of the first voltage and secondvoltage by the detection circuit is carried out when charge/dischargeoperation of the battery unit is stopped.
 14. A battery monitoringsystem according to claim 13, wherein, after termination of thecharge/discharge operation, the detection circuit performs detection ofthe first voltage and second voltage after change of voltage due toinfluence of polarization of battery cells has dropped below apredetermined value.
 15. A battery monitoring system according to claim14, wherein the control circuit does not perform the diagnosis, ifvariation of the voltage does not become less than the predeterminedvalue even after a predetermined time period has elapsed fromtermination of the charge/discharge operation.
 16. A battery monitoringsystem according to claim 15, wherein, if diagnosis has not beenperformed a predetermined number of times in succession after thecharge/discharge operation has been terminated, when thereafter thecharge/discharge operation terminates, the control circuit waits untilvariation of the voltage becomes less than or equal to the predeterminedvalue and, even though the predetermined time period has elapsed, onlyperforms the diagnosis when variation of the voltage becomes less thanor equal to the predetermined value.
 17. A battery monitoring systemaccording to claim 8, further comprising: a first signal transmissionpath which the plurality of integrated circuits are in series connected;a second signal transmission path in which that a first stage integratedcircuit of the in series connected integrated circuits is connected toan external circuit; and a third signal transmission path in which thata last stage integrated circuit of the in series connected integratedcircuits is connected to the external circuit; and wherein theintegrated circuit comprises: a first input circuit for inputting asignal from the external circuit, and a second input circuit forinputting a signal from the integrated circuit which is adjacent; and aninput changeover circuit that: if a signal that is inputted is a signalfrom the external circuit, inputs an output signal from the first inputcircuit to the control circuit; and, if a signal that is inputted is asignal from the integrated circuit which is adjacent, inputs an outputsignal from the second input circuit to the control circuit.
 18. Abattery monitoring system according to claim 8, wherein, when duringdischarge operation of a battery cell by the discharge circuit a cellvoltage measurement of the battery cell is carried out, the integratedcircuit interrupts the discharge operation of the battery cells by thedischarge circuit and measures the cell voltage.
 19. A batterymonitoring system according to claim 1, further comprising: a voltagemeasurement circuit that is provided as the battery state detectioncircuit, and that selects any one of the voltages inputted from aplurality of battery cells connected in series with a selection circuitand measures this voltage that has been selected; and a voltage circuitthat generates a plurality of mutually different voltages as the pseudovoltage information; and wherein the control circuit selects one of themutually different voltages with the selection circuit instead of avoltage of the battery cells, and diagnoses selection state of theselection circuit based on a voltage value measured by the voltagemeasurement circuit.
 20. A battery monitoring system according to claim19, wherein: the voltage circuit comprises a plurality of voltagesources that generate mutually different voltages, and an inputchangeover unit that selects either a voltage of the battery cells or acorresponding voltage of the voltage sources and inputs it to theselection circuit, provided for each of the battery cells; and thecontrol circuit controls by each of the plurality of input changeoverunits, and selects the mutually different voltages with the selectioncircuit, instead of voltages of the battery cells.
 21. A batterymonitoring system according to claim 20, wherein: there is furthercomprised an excessive charge detection circuit that detects excessivecharge by comparing a voltage measured by the voltage measurementcircuit with an excessive charge threshold value, and that outputs thisdetection information to the control circuit; at least one voltage ofthe plurality of voltage sources is set to a voltage that corresponds toexcessive charge; and the control circuit selects with the selectioncircuit, instead of a voltage of the battery cells, the voltage of thevoltage source that is set to a voltage corresponding to excessivecharge, and diagnoses whether or not the excessive charge selectioncircuit is operating normally based on presence or absence of an outputof the detection information at which time.
 22. A battery monitoringsystem according to claim 19, wherein the voltage circuit generates theplurality of mutually different voltages by voltage dividing a voltageof a voltage source with a plurality of resistors that have mutuallydifferent resistance values and that are connected in series.
 23. Abattery monitoring system according to claim 22, wherein: there isfurther comprised an excessive charge detection circuit that detectsexcessive charge by comparing a voltage measured by the voltagemeasurement circuit with an excessive charge threshold value, and thatoutputs this detection information to the control circuit; at least oneof the plurality of resistors is set to a resistance value to provide adivided voltage that corresponds to excessive charge; and the controlcircuit selects with the selection circuit, instead of a voltage of thebattery cells, a divided voltage that include a voltage corresponding toexcessive charge, and diagnoses whether or not the excessive chargeselection circuit is operating normally based on presence or absence ofan output of the detection information at which time.
 24. A batterymonitoring system according to claim 22, wherein the resistance valuesof the plurality of resistors are set so that all of the totals ofdivided voltages of one or any combination of these resistors aremutually different.
 25. A battery monitoring system according to claim22, further comprising: a plurality of short circuit switches, providedto each of the plurality of resistors respectively, that in their closedstates short-circuit both ends of each of the plurality of resistors,and in their open states eliminate the short circuit; and an excessivecharge detection circuit that detects excessive charge by comparing thevoltage measured by the voltage measurement circuit with an excessivecharge threshold value, and that outputs this detection information tothe control circuit; and wherein the control circuit controls openingand closing of the short circuit switches provided respectively to theresistors, takes a divided voltage of the resistors as a voltagecorresponding to excessive charge, and diagnoses whether or not theexcessive charge selection circuit is operating normally based onpresence or absence of an output of the detection information at whichtime.
 26. A battery monitoring system according to claim 22, furthercomprising: a state changeover unit that changes over to any one of afirst connection state in which measurement lines from both positive andnegative electrodes of the battery cells are connected to the selectioncircuit, a second connection state in which both ends of each of theresistors are connected to the selection circuit, and a third connectionstate in which the measurement lines and also both ends of each of theresistors are connected to the selection circuit so that the resistorsand the battery cells are connected in parallel; and an open/closeswitch between the voltage source and the plurality of resistors thatare connected in series; and wherein the control circuit changes overthe state changeover unit to the third connection state along withputting the switch in its opened state, and diagnoses line breakage ofthe measurement lines based on voltage values measured by the voltagemeasurement circuit.
 27. A battery monitoring system according to claim19, further comprising, for each of the plurality of battery cells, adischarge circuit for battery cell charge amount adjustment that isprovided so as to be connected in parallel to the battery cell between apair of measurement lines that connect both positive and negativeelectrodes of the battery cell and the selection circuit; and whereinthe control circuit performs discharge with any one of the plurality ofdischarge circuits, and diagnoses whether line breakage of any of themeasurement lines has occurred, or an output voltage of any one ofbattery cells has become zero, based on voltage values measured by thevoltage measurement circuit.
 28. A battery monitoring system accordingto claim 19, wherein: to each of a plurality of inputs of the selectioncircuit, there is provided a comparison circuit to which are inputted anoutput and an input of the selection circuit to which voltages of theplurality of battery cells are inputted, and that compares whetherdifference between the input and the output is within a predeterminedrange or not; and the control circuit diagnoses selection state of theselection circuit, based on results of comparison by the plurality ofcomparison circuits.
 29. A battery monitoring system according to claim19, wherein: the selection circuit comprises a first selection circuitto which are inputted positive electrode side potentials of theplurality of battery cells and that selects any one of the positiveelectrode side potentials and outputs it to the voltage measurementcircuit, and a second selection circuit to which are inputted negativeelectrode side potentials of the plurality of battery cells and thatselects any one of the negative electrode side potentials and outputs itto the voltage measurement circuit; the voltage circuit comprises: afirst voltage source that generates a first reference potential; a firststate changeover unit that selects either the first reference potentialor the positive electrode side potential that is outputted from thefirst selection circuit, and inputs it to the voltage measurementcircuit; a second voltage source that generates a second referencepotential; and a second state changeover unit that selects either thesecond reference potential or the negative electrode side potential thatis outputted from the second selection circuit, and inputs it to thevoltage measurement circuit; and the control circuit diagnoses theselection state of the first selection circuit by controlling the firstand second state changeover unit so that the second reference potentialis inputted to the voltage management circuit, and diagnoses theselection state of the second selection circuit by controlling the firstand second state changeover unit so that the first reference potentialis inputted to the voltage management circuit.
 30. A battery monitoringsystem according to claim 29, further comprising an excessive chargedetection circuit that detects excessive charge by comparing together avoltage measured by the voltage measurement circuit and an excessivecharge threshold value, and outputs this detection information to thecontrol circuit; and wherein the control circuit diagnoses whether ornot the excessive charge detection circuit is operating normally basedon presence or absence of output of a detection information duringdiagnosis of the first or the second selection circuit.
 31. A diagnosismethod for a battery monitoring system that comprises an excessivecharge detection circuit that detects excessive charge of a battery cellby comparing each cell voltage of a plurality of battery cells that areconnected in series with an excessive charge threshold value, andoutputs detection information, wherein a voltage that corresponds toexcessive charge is inputted to the excessive charge detection circuitinstead of the measured cell voltage, and whether or not the excessivecharge detection circuit is operating normally is diagnosed based onpresence or absence of an output of the detection information.
 32. Adiagnosis method for a battery monitoring system that selects one of aplurality of voltages inputted from a plurality of battery cells thatare connected in series with a selection circuit, measures this selectedvoltage with a voltage measurement circuit, and monitors state of thebattery cell based on the measured voltage, wherein a plurality ofmutually different voltages are generated, a mutually different voltageis selected by the selection circuit instead of a voltage of the batterycell, and state of selection of the selection circuit is diagnosed basedon voltage values measured by the voltage measurement circuit.